import java.io.*;
import java.math.BigInteger;
import java.util.*;
import java.lang.*;
import static java.lang.Math.*;

public class Main implements Runnable {
    public static void main(String[] args) {
        new Thread(null, new Main(), "Check2", 1 << 28).start();// to increse stack size in java
    }
    static long mod = (long) (1e9 + 7);
    public void run() {
        InputReader in = new InputReader(System.in);
        PrintWriter w = new PrintWriter(System.out);


        long  n = in.nextLong();
        long k = in.nextLong();
        long ans= 0;
        for (long i=1;i<=Math.min(100000,n);i++){
            long left = i;
            long right = n-i;
            long sum = left * (left + 1);
            sum /= 2;
            if (sum - right ==k){
                ans = right;
            }
        }
        w.println(ans);

        w.close();
    }
    void debug(Object...args) {
        System.out.println(Arrays.deepToString(args));
    }
    static class pair implements Comparable<pair>{

        int a;
        int b;

        pair(int a,int b){
            this.a = a;
            this.b = b;
        }
        public int compareTo(pair o){
            if(this.b != o.b)return this.b - o.b;
            return this.a - o.a;
        }

    }
    long modinv(long a,long b) {
        long p=power(b,mod-2,mod);

        p=a%mod*p%mod;
        p%=mod;

        return p;

    }
    long power(long x,long y,long mod){
        if(y==0)return 1%mod;
        if(y==1)return x%mod;
        long res=1;
        x=x%mod;
        while(y>0)
        {
            if((y%2)!=0){
                res=(res*x)%mod;
            }
            y=y/2;
            x=(x*x)%mod;
        }
        return res;
    }
    long gcd(long a,long b){

        if(b==0)return a;
        return gcd(b,a%b);
    }
    void sev(int a[],int n){

        for(int i=2;i<=n;i++)a[i]=i;
        for(int i=2;i<=n;i++){

            if(a[i]!=0){
                for(int j=2*i;j<=n;){

                    a[j]=0;
                    j=j+i;
           ... What is the time complexity of the previous code?