source_code: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  
  public class B_574 {
      public static void main(String[] args) throws IOException {
          BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          String[] input = br.readLine().split(" ");
          int N = Integer.valueOf(input[0]);
          int K = Integer.valueOf(input[1]);
          long sum = 0;
          for(int i = 0; i < N; i++){
              if(sum - (N - i) == K){
                  System.out.println(Integer.valueOf(N-i));
                  return;
              }
              sum += (i+1);
          }
          System.out.println("0");
      }
  }
  