source_code: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintWriter;
  import java.util.Scanner;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   *
   * @author Xinyi Tao
   */
  public class Main {
      public static void main(String[] args) {
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          Scanner in = new Scanner(inputStream);
          PrintWriter out = new PrintWriter(outputStream);
          TaskBR574D2 solver = new TaskBR574D2();
          solver.solve(1, in, out);
          out.close();
      }
  
      static class TaskBR574D2 {
          public void solve(int testNumber, Scanner in, PrintWriter out) {
              long n = in.nextLong();
              long k = in.nextLong();
              long r = (long) (Math.sqrt(9 + 8 * (n + k)) - 3) / 2;
              out.println(n - r);
          }
  
      }
  }
  
  