#include <bits/stdc++.h>
using namespace std;
template <typename X>
void MA(X& a, X b) {
  a = max(a, b);
}
template <typename X>
void MI(X& a, X b) {
  a = min(a, b);
}
int DEBUG = 0, MULTI = 0, GCJ = 0;
struct solver_t;
solver_t* solver;
struct solver_t {
  bool is_lucky(int now) {
    int hour = now / 60;
    int min = now % 60;
    return hour % 10 == 7 || min % 10 == 7;
  }
  void solve() {
    int X;
    cin >> X;
    int H, M;
    cin >> H >> M;
    int now = H * 60 + M;
    int times = 0;
    for (; !is_lucky(now); now = (now - X + 60 * 24) % (60 * 24)) {
      times++;
    }
    cout << times << "\n";
  }
  void gen() {}
  void brute() {}
};
int main(int argc, char** argv) {
  for (long long i = (1); i <= (argc - 1); ++i)
    for (int j = 0; argv[i][j]; j++)
      if (argv[i][j] == '.') freopen(argv[i], "r", stdin);
  for (long long i = (1); i <= (argc - 1); ++i)
    if (argv[i] == string("q")) DEBUG = 1 << 30;
  for (long long i = (1); i <= (argc - 1); ++i)
    if (argv[i] == string("gen")) {
      (solver = new solver_t())->gen();
      exit(0);
    }
  for (long long i = (1); i <= (argc - 1); ++i)
    if (argv[i] == string("brute")) {
      (solver = new solver_t())->brute();
      exit(0);
    }
  ios::sync_with_stdio(false), cin.tie(0);
  cout.setf(ios::fixed), cout.precision(10);
  int t;
  if (MULTI || GCJ)
    cin >> t;
  else
    t = 1;
  for (long long i = (1); i <= (t); ++i) {
    if (DEBUG) cerr << 70 << " " << i << endl;
    if (GCJ) cout << "Case #" << i << ": ";
    solver = new solver_t();
    solver->solve();
  }
  return 0;
}
