source_code: import java.util.*;
  import java.io.*;
  
  public class B {
  	
  	public static void main(String[] args) {
  		Scanner sc = new Scanner(System.in);
  		
  		long n = sc.nextInt(), k = sc.nextInt();
  		
  		
  		long start = 1, end = n;
  		
  		while(start <= end) {
  			long mid = (start + end) >> 1;
  			if(calc(mid) - (n - mid) == k) {
  				System.out.println(n - mid);
  				return;
  			} else if (calc(mid) - (n - mid) > k) {
  				end = mid - 1;
  			} else {
  				start = mid + 1;
  			}
  			
  		}
  		
  	}
  	
  	public static long calc(long n) {
  		return (n * n + n) / 2;
  	}
  }
  