source_code: import java.io.*;
  import java.math.BigInteger;
  import java.util.*;
  public class Main {
      static int inf = (int) 1e9;
      public static void main(String[] args) throws IOException {
          br = new BufferedReader(new InputStreamReader(System.in));
          pw = new PrintWriter(System.out);
          int n = nextInt();
          int k = nextInt();
          long l = -1;
          long r = 100000;
          while(l != r - 1) {
              long mid = (l + r) / 2;
              if (mid * (mid + 1) / 2 - (n - mid) > k) r = mid;
              else l = mid;
          }
          pw.println(n - l);
          pw.close();
      }
  
      static BufferedReader br;
      static StringTokenizer st = new StringTokenizer("");
      static PrintWriter pw;
  
      static String next() throws IOException {
          while (!st.hasMoreTokens()) st = new StringTokenizer(br.readLine());
          return st.nextToken();
      }
  
      static int nextInt() throws IOException {
          return Integer.parseInt(next());
      }
  
      static long nextLong() throws IOException {
          return Long.parseLong(next());
      }
      static Double nextDouble() throws IOException {
          return Double.parseDouble(next());
      }
  }