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: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.math.BigInteger;
  import java.util.*;
  
  public class Practice {
  	public static long mod = (long) Math.pow(10, 9) + 7;
  	public static long mod2 = 998244353;
  	public static int tt = 1;
  	public static ArrayList<Integer> prime;
  	public static long[] fac = new long[200005];
  	public static long[] invfac = new long[200005];
  
  	public static void main(String[] args) throws Exception {
  
  		PrintWriter pw = new PrintWriter(System.out);
  		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  		int t = Integer.valueOf(br.readLine());
  		while (t-- > 0) {
  			String[] s1 = br.readLine().split(" ");
  			long n = Integer.parseInt(s1[0]);
  			long m = Integer.parseInt(s1[1]);
  			int a = 0;
  			for (int i = 31; i >= 0; i--) {
  				// System.out.println((m >> i) & 1);
  				if (((m >> i) & 1) == 0 && ((n >> i) & 1) == 1) {
  					m = m | (1 << i);
  					a = 1;
  
  				} else if (a == 1) {
  					// System.out.println(m+" "+i);
  					if (((n >> i) & 1) == 0) {
  						if (((m >> i) & 1) == 1) {
  							m = m ^ (1 << i);
  						}
  					}
  
  				}
  			}
  			if (a == 0) {
  				for (int i = 0; i < 32; i++) {
  					// System.out.println((m >> i) & 1);
  					if (((m >> i) & 1) == 0) {
  						m = m | (1 << i);
  						a = 1;
  						for (int j = i - 1; j >= 0; j--) {
  							// System.out.println((m >> i) & 1);
  							if (((m >> j) & 1) == 0 && ((n >> j) & 1) == 1) {
  								m = m | (1 << i);
  
  							} else if (a == 1) {
  								// System.out.println(m+" "+i);
  								if (((n >> j) & 1) == 0) {
  									if (((m >> j) & 1) == 1) {
  										m = m ^ (1 << j);
  									}
  								}
  
  							}
  						}
  						a = 1;
  						break;
  					}
  				}
  			}
  			// 11110001001000000
  			// 10011111101111110001
  
  			// System.out.println(m);
  			pw.println(n ^ m);
  		}
  		pw.close();
  
  	}
  
  	// private static int kmp(String str) {
  //		// TODO Auto-generated method stub
  //		// System.out.println(str);
  //		int[] pi = new int[str.length()];
  //		pi[0] = 0;
  //		for (int i = 1; i < str.length(); i++) {
  //			int j = pi[i - 1];
  //			while (j > 0 && str.charAt(i) != str.charAt(j)) {
  //				j = pi[j - 1];
  //			}
  //			if (str.charAt(j) == str.charAt(i)) {
  //				j++;
  //			}
  //			pi[i] = j;
  //			System.out.print(pi[i]);
  //		}
  //		System.out.println();
  //		return pi[str.length() - 1];
  //	}
  
  }
  
  //	private static void getFac(long n, PrintWriter pw) {
  //		// TODO Auto-generated method stub
  //		int a = 0;
  //		while (n % 2 == 0) {
  //			a++;
  //			n = n / 2;
  //		}
  //		if (n == 1) {
  //			a--;
  //		}
  //		for (int i = 3; i <= Math.sqrt(n); i += 2) {
  //			while (n % i == 0) {
  //				n = n / i;
  //				a++;
  //			}
  //		}
  //		if (n > 1) {
  //			a++;
  //		}
  //		if (a % 2 == 0) {
  //			pw.println("Bob");
  //		} else {
  //			pw.println("Alice");
  //		}
  //		//System.out.println(a);
  //		return;
  //	}
  
  //	private static long power(long a, long p) {
  //		// TODO Auto-generated method stub
  //		long res = 1;
  //		while (p > 0) {
  //			if (p % 2 == 1) {
  //				res = (res * a) % mod;
  //			}
  //			p = p / 2;
  //			a = (a * a) % mod;
  //		}
  //		return res;
  //	}
  //
  //	private static void fac() {
  //		fac[0] = 1;
  //		// TODO Auto-generated method stub
  //		for (int i = 1; i < fac.length; i++) {
  //			if (i == 1) {
  //				fac[i] = 1;
  //			} else {
  //				fac[i] = i * fac[i - 1];
  //			}
  //			if (fac[i] > mod) {
  //				fac[i] = fac[i] % mod;
  //			}
  //		}
  //	}
  //
  //	private static int getLower(Long long1, Long[] st) {
  //		// TODO Auto-generated method stub
  //		int left = 0, right = st.length - 1;
  //		int ans = -1;
  //		while (left <= right) {
  //			int mid = (left + right) / 2;
  //			if (st[mid] <= long1) {
  //				ans = mid;
  //				left = mid + 1;
  //			} else {
  //				right = mid - 1;
  //			}
  //		}
  //		return ans;
  //	}
  
  //	private static long getGCD(long l, long m) {
  //
  //		long t1 = Math.min(l, m);
  //		long t2 = Math.max(l, m);
  //		while (true) {
  //			long temp = t2 % t1;
  //			if (temp == 0) {
  //				return t1;
  //			}
  //			t2 = t1;
  //			t1 = temp;
  //		}
  //	}