#include <bits/stdc++.h>
using namespace std;
vector<double> v;
int main() {
  int n, k;
  cin >> n >> k;
  int T = 240 - k;
  v.push_back(0);
  for (int i = 1; i <= n; i++) {
    v.push_back(i * 5);
    v[i] = v[i - 1] + v[i];
  }
  int L = 0, Hi = n, mid, res = 0;
  while (L <= Hi) {
    mid = (L + Hi) / 2;
    if (v[mid] <= T) {
      L = mid + 1;
      res = max(mid, res);
    } else {
      Hi = mid - 1;
    }
  }
  cout << res << "\n";
  return 0;
}
