source_code: import java.io.*;
  import java.util.StringTokenizer;
  
  public class Main {
  
      public static void main(String[] args) throws IOException {
          Scanner sc = new Scanner(System.in);
          PrintWriter out = new PrintWriter(System.out);
          int n = sc.nextInt(), k = sc.nextInt();
          long rhs = 2l * (n + k);
          for (int x = 1; ; x++) {
              long lhs = 1l * x * x + 3l * x;
              if (rhs == lhs) {
                  out.println(n - x);
                  break;
              }
          }
          out.flush();
          out.close();
      }
  
  
      static class Scanner {
          StringTokenizer st;
          BufferedReader br;
  
          public Scanner(InputStream system) {
              br = new BufferedReader(new InputStreamReader(system));
          }
  
  
          public String next() throws IOException {
              while (st == null || !st.hasMoreTokens()) st = new StringTokenizer(br.readLine());
              return st.nextToken();
          }
  
          public String nextLine() throws IOException {
              return br.readLine();
          }
  
          public int nextInt() throws IOException {
              return Integer.parseInt(next());
          }
  
          public double nextDouble() throws IOException {
              return Double.parseDouble(next());
          }
  
          public char nextChar() throws IOException {
              return next().charAt(0);
          }
  
          public Long nextLong() throws IOException {
              return Long.parseLong(next());
          }
  
          public boolean ready() throws IOException {
              return br.ready();
          }
  
  
          public int[] nextIntArray(int n) throws IOException {
              int[] a = new int[n];
              for (int i = 0; i < n; i++)
                  a[i] = nextInt();
              return a;
          }
  
          public long[] nextLongArray(int n) throws IOException {
              long[] a = new long[n];
              for (int i = 0; i < n; i++)
                  a[i] = nextLong();
              return a;
          }
  
  
          public Integer[] nextIntegerArray(int n) throws IOException {
              Integer[] a = new Integer[n];
              for (int i = 0; i < n; i++)
                  a[i] = nextInt();
              return a;
          }
  
          public double[] nextDoubleArray(int n) throws IOException {
              double[] ans = new double[n];
              for (int i = 0; i < n; i++)
                  ans[i] = nextDouble();
              return ans;
          }
  
          public short nextShort() throws IOException {
              return Short.parseShort(next());
          }
  
      }
  }