source_code: import java.util.Scanner;
  
  public class Main {
  	
  	public static void main(String[] args)
  	{
  		Scanner s=new Scanner(System.in);
  		
  		double n=s.nextLong();
  		double k=s.nextLong();
  		
  		double num=(-3+Math.sqrt(9+8*(n+k)))/2;
  		
  		System.out.println((long)(n-num));
  		
  	}
  	
  }