#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, i = 0;
  cin >> n >> k;
  k = 240 - k;
  while (1) {
    if (5 * (i + 1) > k || i + 1 > n) break;
    i++;
    k -= 5 * i;
  }
  cout << i << endl;
  return 0;
}
