#include <bits/stdc++.h>
using namespace std;
inline void file() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  if (0) {
    freopen(".in", "r", stdin);
    freopen(".out", "w", stdout);
  }
}
const clock_t MAXT = (100 * CLOCKS_PER_SEC) / 1000;
const int PX[8] = {1, 0, -1, 0, 1, 1, -1, -1},
          PY[8] = {0, 1, 0, -1, -1, 1, 1, -1}, N = 1e5 + 10, INF = 1e9,
          MOD = 1e9 + 7;
const long long INFL = 1e18, MODL = 1e9 + 7;
const long double EPS = 1e-9;
inline int rnd(int l = 0, int r = INF) {
  unsigned ans = rand();
  ans = (ans << 8) ^ rand();
  ans = (ans << 8) ^ rand();
  ans = (ans << 8) ^ rand();
  ans %= r - l + 1;
  return int(ans + l);
}
inline bool good(int x) {
  int h, m;
  h = x / 60;
  m = x % 60;
  if (h % 10 == 7 || m % 10 == 7) return true;
  return false;
}
int main() {
  file();
  int x, h, m, t;
  cin >> x >> h >> m;
  t = h * 60 + m;
  for (int i = 0;; i++) {
    if (good(t)) {
      cout << i;
      return 0;
    } else
      cerr << t / 60 << ' ' << t % 60 << '\n';
    t = (t + 1440 - x) % 1440;
  }
}
