source_code: // CodeForces Round #914 B train done
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  
  public class SportMafia {
  	
  	int n,k;
  	int nCand;
  
  	private void readData(BufferedReader bin) throws IOException {
  		String s = bin.readLine();
  		String []ss = s.split(" ");
  		n = Integer.parseInt(ss[0]);
  		k = Integer.parseInt(ss[1]);
  	}
  
  	void printRes() {
  		System.out.println(nCand);
  	}	
  	
  	private void calculate() {
  		// count napitki
  		double p;
  		p = -1.5 + Math.sqrt(2.25 + 2.0*(n+k));
  		nCand = (int)Math.round(n-p);
  	}
  	
  	public static void main(String[] args) throws IOException {
  		// BufferedReader bin = new BufferedReader(new FileReader("cactus.in"));
  		BufferedReader bin = new BufferedReader(
  				new InputStreamReader(System.in));
  		SportMafia l = new SportMafia();
  		l.readData(bin);
  		l.calculate();
  		l.printRes();
  	}
  }
  