source_code: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintWriter;
  import java.io.IOException;
  import java.io.InputStream;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   *
   * @author Aman Kumar Singh
   */
  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 {
          int MAXN = 200005;
          PrintWriter out;
          InputReader in;
  
          public void solve(int testNumber, InputReader in, PrintWriter out) {
              this.out = out;
              this.in = in;
              long n = nl();
              long k = nl();
              long i = 0;
              k += n;
              for (i = 0; i < MAXN; i++) {
                  long x = (i * (i + 3)) / 2;
                  if (k == x) {
                      pn(n - i);
                      return;
                  }
              }
  
          }
  
          long nl() {
              return in.nextLong();
          }
  
          void pn(long zx) {
              out.println(zx);
          }
  
      }
  
      static class InputReader {
          private InputStream stream;
          private byte[] buf = new byte[1024];
          private int curChar;
          private int numChars;
  
          public InputReader(InputStream stream) {
              this.stream = stream;
          }
  
          public int read() {
              if (numChars == -1) {
                  throw new UnknownError();
              }
              if (curChar >= numChars) {
                  curChar = 0;
                  try {
                      numChars = stream.read(buf);
                  } catch (IOException e) {
                      throw new UnknownError();
                  }
                  if (numChars <= 0) {
                      return -1;
                  }
              }
              return buf[curChar++];
          }
  
          public long nextLong() {
              return Long.parseLong(next());
          }
  
          public String next() {
              int c = read();
              while (isSpaceChar(c)) {
                  c = read();
              }
              StringBuffer res = new StringBuffer();
              do {
                  res.appendCodePoint(c);
                  c = read();
              } while (!isSpaceChar(c));
  
              return res.toString();
          }
  
          private boolean isSpaceChar(int c) {
              return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
          }
  
      }
  }
  
  