source_code: import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.io.StreamTokenizer;
  import java.util.Scanner;
  
  public class Main {
  	static StreamTokenizer st = new StreamTokenizer(new BufferedInputStream(System.in));
  	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  	static PrintWriter pr = new PrintWriter(new BufferedOutputStream(System.out));
  	static Scanner sc = new Scanner(System.in);
  
  	public static void main(String[] args) throws NumberFormatException, IOException {
  		int a = sc.nextInt();
  		int b = sc.nextInt();
  		int i = 0;
  		int cont = 0;
  		while(cont<b) {
  			i++;
  			cont+=i;
  		}
  		
  		if(i+cont-b==a) {
  			System.out.println(cont-b);
  		}else {
  			while(i+cont-b!=a) {
  				i++;
  				cont+=i;
  			}
  			System.out.println(cont-b);
  		}
  	}
  
  	private static int nextInt() {
  		try {
  			st.nextToken();
  		} catch (IOException e) {
  			e.printStackTrace();
  		}
  		return (int) st.nval;
  	}
  }
  