description: You are given two integers n and m. Find the \operatorname{MEX} of the sequence n ⊕ 0, n ⊕ 1, …, n ⊕ m. Here, ⊕ is the [bitwise XOR operator](https://en.wikipedia.org/wiki/Bitwise_operation#XOR).
  
  \operatorname{MEX} of the sequence of non-negative integers is the smallest non-negative integer that doesn't appear in this sequence. For example, \operatorname{MEX}(0, 1, 2, 4) = 3, and \operatorname{MEX}(1, 2021) = 0. 
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 30 000) — the number of test cases.
  
  The first and only line of each test case contains two integers n and m (0 ≤ n, m ≤ 10^9).
  
  Output
  
  For each test case, print a single integer — the answer to the problem.
  
  Example
  
  Input
  
  
  5
  3 5
  4 6
  3 2
  69 696
  123456 654321
  
  
  Output
  
  
  4
  3
  0
  640
  530866
  
  Note
  
  In the first test case, the sequence is 3 ⊕ 0, 3 ⊕ 1, 3 ⊕ 2, 3 ⊕ 3, 3 ⊕ 4, 3 ⊕ 5, or 3, 2, 1, 0, 7, 6. The smallest non-negative integer which isn't present in the sequence i. e. the \operatorname{MEX} of the sequence is 4.
  
  In the second test case, the sequence is 4 ⊕ 0, 4 ⊕ 1, 4 ⊕ 2, 4 ⊕ 3, 4 ⊕ 4, 4 ⊕ 5, 4 ⊕ 6, or 4, 5, 6, 7, 0, 1, 2. The smallest non-negative integer which isn't present in the sequence i. e. the \operatorname{MEX} of the sequence is 3.
  
  In the third test case, the sequence is 3 ⊕ 0, 3 ⊕ 1, 3 ⊕ 2, or 3, 2, 1. The smallest non-negative integer which isn't present in the sequence i. e. the \operatorname{MEX} of the sequence is 0.
solution: 					/*
  					TO LEARN
  					1-segment trees
  					2-euler tour
  				
  					*/
  					/*
  					TO SOLVE 
  					uva 1103
  					codeforces 722 kavi on pairing duty
  					*/
  					/*
  					bit manipulation shit
  					1-Computer Systems: A Programmer's Perspective
  					2-hacker's delight
  					3-(02-03-bits-ints)
  					4-machine-basics
  					5-Bits Manipulation tutorialspoint
  					*/
  					/*
  					TO WATCH
  					1-what is bitmasking by kartik arora youtube
  					*/
  					            import java.util.*;
  							    import java.math.*;
  							    import java.io.*; 
  							    import java.util.stream.Collectors;
  
  							       public class A{
  							     
  							  static InputStream inputStream = System.in;
  					            static FastScanner scan=new FastScanner();
  							     public static PrintWriter out = new PrintWriter (new BufferedOutputStream(System.out));
  static long l,r;
  static long dp[][][][][];
  static int len;
  static int put(int st,int a,int b)
  {
  	if(st==0)
  	{
  		if(a==b)
  			return 0;
  		if(a<b)
  			return 1;
  		else return 2;
  	}
  	return st;
  }
  static long rec(int i,int f1,int s1,int f2,int s2)
  {
  
  	//System.out.println(ff+" "+ss);
  
  	if(i<0){
  		if((f1==0||f1==2)&&(s1==1||s1==0)&&(f2==0||f2==2)&&(s2==1||s2==0)){
  	//out.println("FUCK");
  		return 0;
  	}
  	//out.println(i);
  	return (long)-(1e19+5000);
  	}
  	/*
  	i can make 4 things 
  	1-0 1
  	2-1 0
  	3-0 0
  	4-1 1
  	*/
  	if(dp[i][f1][s1][f2][s2]!=-1)
  		return dp[i][f1][s1][f2][s2];
  
  	long toadd;
  	toadd=(1L<<i);
  	//out.println(toadd);
  	int bit=(int)((l>>i)&1);
  	int bit2=(int)((r>>i)&1);
  	int tmp1,tmp2,tmp11,tmp22;
  	long res=(long)-(1e19+5000);
  	res=Math.max(res,rec(i-1,put(f1,0,bit),put(s1,0,bit2),put(f2,1,bit),put(s2,1,bit2))+toadd);
  	res=Math.max(res,rec(i-1,put(f1,1,bit),put(s1,1,bit2),put(f2,0,bit),put(s2,0,bit2))+toadd);
  //	out.println(res);
  	res=Math.max(res,rec(i-1,put(f1,0,bit),put(s1,0,bit2),put(f2,0,bit),put(s2,0,bit2)));
  	res=Math.max(res,rec(i-1,put(f1,1,bit),put(s1,1,bit2),put(f2,1,bit),put(s2,1,bit2)));
  	return dp[i][f1][s1][f2][s2]=res;
  	
  
  }
  
  						public static void main(String[] args)  throws Exception 
  					      {
  					 
  
  								///scan=new FastScanner("cownomics.in");
  							//out = new PrintWriter("cownomics.out");
  							 
  							 /*
  							 currently doing 
  							 1-digit dp
  							 2-ds like fenwick and interval tree and sparse table 
  							 */
  							 /*
  							 READING 
  							 1-Everything About Dynamic Programming codeforces
  							 2-DYNAMIC PROGRAMMING: FROM NOVICE TO ADVANCED topcoder
  							 3-Introduction to DP with Bitmasking codefoces
  							 4-Bit Manipulation hackerearth
  							 5-read more about mobious and inculsion-exclusion 
  							 */
  		
  
  							    int tt=1;
  							   //System.out.println(131072^366525);						
  					tt=scan.nextInt();
  
  
  						 outer:while(tt-->0)
  							    {
  							    
  			long n=scan.nextLong(),m=scan.nextLong();
  			long res=Long.MAX_VALUE;
  			for(int pos=31;pos>=0;pos--){
  				if(((m>>pos)&1)!=0)
  					continue;
  			long cur=0;
  			for(long i=31;i>pos;i--)
  			{
  				
  				if(((m>>i)&1)==0&&((n>>i)&1)!=0)
  						cur+=(1L<<i);
  					else if(((m>>i)&1)!=0&&((n>>i)&1)==0)
  						cur+=(1L<<i);
  			}
  			if(((n>>pos)&1)==0)
  				cur+=(1<<pos);
  			if((cur^n)>m)
  					res=Math.min(res,cur);
  		}
  			out.println(res);
  				
  		
  
  	}
  	out.close();
  				}
  	    
  							static class special{
  								boolean bool;
  								long n;
  								//int id;
  								special(boolean bool,long n)
  								{
  									this.bool=bool;
  									this.n=n;
  								}
  								@Override
  								    public int hashCode() {
  							                int hash = 7;
  				    hash = 31 * hash + (int) n;
  				   
  				    return hash;
  							            }
  							              @Override
  							            public boolean equals(Object o){
  							                if (o == this) return true;
  							                if (o.getClass() != getClass()) return false;
  							                special t = (special)o;
  							                return t.bool == bool && t.n == n;
  							            }
  							}
  
  							   
  							     static long binexp(long a,long n)
  							    {
  							        if(n==0)
  							            return 1;
  							        long res=binexp(a,n/2);
  							        if(n%2==1)
  							            return res*res*a;
  							        else 
  							            return res*res;
  							    }
  							     
  							    static long powMod(long base, long exp, long mod) {
  							           if (base == 0 || base == 1) return base;
  							           if (exp == 0) return 1;
  							           if (exp == 1) return (base % mod+mod)%mod;
  							           long R = (powMod(base, exp/2, mod) % mod+mod)%mod;
  							           R *= R;
  							           R %= mod;
  							           if ((exp & 1) == 1) {
  							               return (base * R % mod+mod)%mod;
  							           }
  							           else return (R %mod+mod)%mod;
  							       }
  							    static double dis(double x1,double y1,double x2,double y2)
  							    {
  							        return Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
  							    }
  							    static long mod(long x,long y)
  							        {
  							            if(x<0)
  							                x=x+(-x/y+1)*y;
  							            return x%y;
  							        }
  							     public static  long pow(long b, long e) {
  							                long r = 1;
  							                while (e > 0) {
  							                    if (e % 2 == 1) r = r * b ;
  							                    b = b * b;
  							                    e >>= 1;
  							                }
  							                return r;
  							            }
  							    private static void sort(long[] arr) {
  							            List<Long> list = new ArrayList<>();
  							            for (long object : arr) list.add(object);
  							            Collections.sort(list);
  							        //Collections.reverse(list);
  							            for (int i = 0; i < list.size(); ++i) arr[i] = list.get(i);
  							        }
  							    private static void sort2(long[] arr) {
  							            List<Long> list = new ArrayList<>();
  							            for (Long object : arr) list.add(object);
  							            Collections.sort(list);
  							        Collections.reverse(list);
  							            for (int i = 0; i < list.size(); ++i) arr[i] = list.get(i);
  							        }
  							     static class FastScanner
  					{
  					    private int BS = 1 << 16;
  					    private char NC = (char) 0;
  					    private byte[] buf = new byte[BS];
  					    private int bId = 0, size = 0;
  					    private char c = NC;
  					    private double cnt = 1;
  					    private BufferedInputStream in;
  					 
  					    public FastScanner() {
  					        in = new BufferedInputStream(System.in, BS);
  					    }
  					 
  					    public FastScanner(String s) {
  					        try {
  					            in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
  					        } catch (Exception e) {
  					            in = new BufferedInputStream(System.in, BS);
  					        }
  					    }
  					 
  					    private char getChar() {
  					        while (bId == size) {
  					            try {
  					                size = in.read(buf);
  					            } catch (Exception e) {
  					                return NC;
  					            }
  					            if (size == -1) return NC;
  					            bId = 0;
  					        }
  					        return (char) buf[bId++];
  					    }
  					 
  					    public int nextInt() {
  					        return (int) nextLong();
  					    }
  					 
  					    public int[] nextInts(int N) {
  					        int[] res = new int[N];
  					        for (int i = 0; i < N; i++) {
  					            res[i] = (int) nextLong();
  					        }
  					        return res;
  					    }
  					 
  					    public long[] nextLongs(int N) {
  					        long[] res = new long[N];
  					        for (int i = 0; i < N; i++) {
  					            res[i] = nextLong();
  					        }
  					        return res;
  					    }
  					 
  					    public long nextLong() {
  					        cnt = 1;
  					        boolean neg = false;
  					        if (c == NC) c = getChar();
  					        for (; (c < '0' || c > '9'); c = getChar()) {
  					            if (c == '-') neg = true;
  					        }
  					        long res = 0;
  					        for (; c >= '0' && c <= '9'; c = getChar()) {
  					            res = (res << 3) + (res << 1) + c - '0';
  					            cnt *= 10;
  					        }
  					        return neg ? -res : res;
  					    }
  					 
  					    public double nextDouble() {
  					        double cur = nextLong();
  					        return c != '.' ? cur : cur + nextLong() / cnt;
  					    }
  					 
  					    public double[] nextDoubles(int N) {
  					        double[] res = new double[N];
  					        for (int i = 0; i < N; i++) {
  					            res[i] = nextDouble();
  					        }
  					        return res;
  					    }
  					 
  					    public String next() {
  					        StringBuilder res = new StringBuilder();
  					        while (c <= 32) c = getChar();
  					        while (c > 32) {
  					            res.append(c);
  					            c = getChar();
  					        }
  					        return res.toString();
  					    }
  					 
  					    public String nextLine() {
  					        StringBuilder res = new StringBuilder();
  					        while (c <= 32) c = getChar();
  					        while (c != '\n') {
  					            res.append(c);
  					            c = getChar();
  					        }
  					        return res.toString();
  					    }
  					 
  					    public boolean hasNext() {
  					        if (c > 32) return true;
  					        while (true) {
  					            c = getChar();
  					            if (c == NC) return false;
  					            else if (c > 32) return true;
  					        }
  					    }
  					}
  
  							     static class Pair implements Comparable<Pair>{
  							            public long x, y,z;
  							            public Pair(long x1, long y1,long z1) {
  							                x=x1;
  							                y=y1;
  							                z=z1;
  							            }
  							             public Pair(long x1, long y1) {
  							                x=x1;
  							                y=y1;
  							    
  							            }
  							            
  							            @Override
  							            public int hashCode() {
  							                return (int)(x + 31 * y);
  							            }
  							            public String toString() {
  							                return x + " " + y+" "+z;
  							            }
  							            @Override
  							            public boolean equals(Object o){
  							                if (o == this) return true;
  							                if (o.getClass() != getClass()) return false;
  							                Pair t = (Pair)o;
  							                return t.x == x && t.y == y&&t.z==z;
  							            }
  							    public int compareTo(Pair o)
  							    {
  							    	
  							    
  							    	return (int)(o.y-y);
  							     
  							        }
  							     
  							    }
  							    
  							    }
  
  							     
  