#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  double time, sum;
  cin >> n >> k;
  time = 240 - double(k);
  time = time / 5;
  for (int i = 1; i <= n + 1; i++) {
    sum = (i * (i + 1)) / double(2);
    if (sum > time) {
      cout << i - 1;
      return 0;
    }
  }
  cout << n;
  return 0;
}
