#include <bits/stdc++.h>
using namespace std;
int main() {
  long long i, j, n, k, total = 0, time1 = 240;
  vector<long long> v;
  cin >> n >> k;
  for (i = 1; i <= n; i++) {
    v.push_back(5 * i);
    total += v[i - 1];
  }
  while ((time1 - total) < k) {
    total -= v[n - 1];
    n--;
  }
  cout << n << endl;
}
