source_code: import java.util.*;
  public class CFEdu66 {
  
  	public static void main(String[] args) {
  		Scanner in = new Scanner(System.in);
  		long n = in.nextLong();
  		long k = in.nextLong();
  		double tmp = Math.sqrt(9 + 8*(n+k));
  		if(Math.ceil(tmp)-tmp<0.001)
  			tmp = Math.ceil(tmp);
  		
  		long root = (long)tmp;
  		long x = (-3+root)/2;
  		System.out.println(n-x);
  		
  	}
  
  }
  