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

int32_t main()
{
    ios::sync_with_stdio(false), cin.tie(nullptr);
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    int p; cin >> p;
    int64_t l = 1, r = INT_MAX, it = 300, ans = INT_MAX;
    bool found = 0;
    while (it--) {
        int64_t a = (l + r) / 2;
        int64_t cnt = 0, i = 5;
        while (a / i) cnt += a / i, i *= 5;
        if (cnt >= p) {
            if (cnt == p) ans = min(ans, a), found = 1;
            r = a;
        } else {
            l = a;
        } 
    }
    cout << (found ? ans : -1);
    return 0;
}