#include <bits/stdc++.h>
using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int p;
    fin >> p;
    int left = 1, right = 1e9, answer = -1;
    while (left <= right) {
        int zeros = 0, mid = (left + right) / 2;
        for (int i = 5; i <= mid; i *= 5) {
            zeros += mid / i;
        }
        if (zeros == p) {
            answer = mid;
            right = mid - 1;
        } else if (zeros > p) {
            right = mid - 1;
        } else {
            left = mid + 1;
        }
    }
    fout << answer;
    return 0;
}