source_code: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  import java.io.IOException;
  import java.io.BufferedReader;
  import java.io.InputStreamReader;
  import java.io.InputStream;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   *
   * @author Jaynil
   */
  public class Main {
      public static void main(String[] args) {
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          InputReader in = new InputReader(inputStream);
          PrintWriter out = new PrintWriter(outputStream);
          BSportMafia solver = new BSportMafia();
          solver.solve(1, in, out);
          out.close();
      }
  
      static class BSportMafia {
          public void solve(int testNumber, InputReader in, PrintWriter out) {
              long n = in.nextLong();
              long k = in.nextLong();
              long b = 2 * n + 3;
              long c = n * n - 2 * k + n;
              long d = b * b - 4 * c;
              long val = (b - (long) Math.sqrt(d)) / 2;
  
              out.println(val);
          }
  
      }
  
      static class InputReader {
          public BufferedReader reader;
          public StringTokenizer tokenizer;
  
          public InputReader(InputStream stream) {
              reader = new BufferedReader(new InputStreamReader(stream), 32768);
              tokenizer = null;
          }
  
          public String next() {
              while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                  try {
                      tokenizer = new StringTokenizer(reader.readLine());
                  } catch (IOException e) {
                      throw new RuntimeException(e);
                  }
              }
              return tokenizer.nextToken();
          }
  
          public long nextLong() {
              return Long.parseLong(next());
          }
  
      }
  }
  
  