#include <stdio.h>

int P;

int nr_zeros(int N) {
  long long ret = 0;
  for (long long p = 5; p <= N; p = p * 5) {
    ret = ret + N / p;
  }

  return ret;
}

int main() {
  freopen("fact.in", "r", stdin);
  freopen("fact.out", "w", stdout);

  scanf("%d ", &P);

  int st = 1, dr = P * 15;

  while (st < dr - 1) {
    int mid = st + (dr - st + 1) / 2;
    if (nr_zeros(mid) >= P) {
      dr = mid;
    } else {
      st = mid;
    }
  }

  if (nr_zeros(st) < P) {
    printf("%d ", dr);
  } else {
    printf("%d ", st);
  }

  return 0;
}