
import java.math.*;
import java.util.*;
import java.io.*;
public class Main{
    static StreamTokenizer in=new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
    static BufferedReader buffer=new BufferedReader(new InputStreamReader(System.in));
    static Scanner sc=new Scanner(System.in);
    static PrintWriter out=new PrintWriter(System.out);
    //static InputReader sc=new InputReader(System.in);
    static final int inf=10000000;
    public static void main(String args[])throws Exception {
        double n,k;
        n=sc.nextDouble();
        k=sc.nextDouble();
        double ans=0;
        ans=Math.sqrt(2.25+2*(n+k))-1.5;
        System.out.printf("%.0f\n",n-ans);
    }
    static void ssort(int arr[]){
        int len=arr.length;
        for(int i=0;i<len;i++){
            int t=(int)(len*Math.random());
            int temp=arr[t];
            arr[t]=arr[i];
            arr[i]=temp;
        }
        Arrays.sort(arr);
    }
    static int getInt()throws Exception{
        in.nextToken();
        return  (int)in.nval;
    }
}

class InputReader {
    private final InputStream stream;
    private final byte[] buf = new byte[8192];
    private int curChar, snumChars;
    public InputReader(InputStream st) {
        this.stream = st;
    }
    public int read() {
        if (snumChars == -1)
            throw new InputMismatchException();
        if (curChar >= snumChars) {
            curChar = 0;
            try {
                snumChars = stream.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (snumChars <= 0)
                return -1;
        }
        return buf[curChar++];
    }

    public int nextInt() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }

    public long nextLong() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }

    public int[] nextIntArray(int n) {
        int a[] = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = nextInt();
        }
        return a;
    }

    public String readString() {
        int c = read();
        while (isSpaceChar(c)) {
            c = read();
        }
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }

    public String nextLine() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isEndOfLine(c));
        return res.toString();
    }

    public boolean isSpaceChar(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }

    private boolean isEndOfLine(int c) {
        return c == '\n' || c == '\r' || c == -1;
    }

}
/*




 */