#include <bits/stdc++.h>
inline bool EQ(double a, double b) { return fabs(a - b) < 1e-9; }
const int INF = 1 << 29;
inline int two(int n) { return 1 << n; }
inline int test(int n, int b) { return (n >> b) & 1; }
inline void setBit(int& n, int b) { n |= two(b); }
inline void unsetBit(int& n, int b) { n &= ~two(b); }
inline int last_bit(int n) { return n & (-n); }
inline int ones(int n) {
  int res = 0;
  while (n && ++res) n -= n & (-n);
  return res;
}
inline bool sortDown(int x, int y) { return x > y; }
template <class T>
void chmax(T& a, const T& b) {
  a = max(a, b);
}
template <class T>
void chmin(T& a, const T& b) {
  a = min(a, b);
}
using namespace std;
int main() {
  std::ios::sync_with_stdio(false);
  int n;
  cin >> n;
  int k;
  cin >> k;
  int total = 4 * 60;
  total -= (k);
  int prob = 0;
  for (int i = (1); i <= (n); i++) {
    prob += 5 * i;
    if (prob > total) {
      cout << (i - 1) << endl;
      return 0;
    }
  }
  cout << n << endl;
  return 0;
}
