#include <bits/stdc++.h>
int n, K;
int sum;
int main() {
  scanf("%d%d", &n, &K);
  K = 240 - K;
  for (int i = 1; i <= n; i++) {
    sum += i * 5;
    if (sum > K) {
      printf("%d\n", i - 1);
      return 0;
    }
  }
  printf("%d\n", n);
}
