#include <iostream>

int main() {

  int n, k, time_ = 0, solved = 0;

  std::cin >> n >> k;

  while ((time_ + 5 * (solved + 1) <= 60 * 4 - k) and (solved < n)) {

      solved += 1;

      time_ += solved * 5;

  }

  std::cout << solved;

  return 0;

}