source_code: import java.io.*;
  import java.util.*;
  
  public class F {
      public static void main(String[] args) throws IOException {
          BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
          PrintWriter writer = new PrintWriter(System.out);
          StringTokenizer st = new StringTokenizer(reader.readLine());
          long n = Integer.parseInt(st.nextToken());
          long k = Integer.parseInt(st.nextToken());
          long l = 0;
          long r = n;
          while(l <= r){
              long min = (l + r) / 2;
              if((min * (min + 1) / 2 - (n - min) == k)){
                  System.out.println(n - min);
                  return;
              }
              else if((min * (min + 1) / 2 - (n - min) > k)){
                  r = min - 1;
              }
              else{
                  l = min + 1;
              }
          }
      }
  }