source_code: import java.util.*;
  import java.io.*;
  
  public class candies {
  	public void run() throws Exception {
  		Scanner file = new Scanner(System.in);
  		int actions = file.nextInt();
  		int left = file.nextInt();
  		int start = 0;
  		int c = 1;
  		while (true) {
  			start += c;
  			if (c + (start - left) == actions) break;
  			c++;
  		}
  		System.out.println(start - left);
  	}
  
  	public static void main(String[] args) throws Exception {
  		new candies().run();
  	}
  
  }