#include <fstream>
#include<cmath>

using namespace std;

long long int factori_5(long long int x) {
    int cnt = 0;
    while (x > 0) {
        if (x % 5 == 0) {
            x /= 5;
            cnt++;
        }
        if (x % 5 != 0)
            break;
    }
    return cnt;
}

int main() {
    ifstream cin("fact.in");
    ofstream cout("fact.out");
    int p;
    cin >> p;
    long long int r = 0;
    long long i = 5;
    if (p == 0)
        cout << 1;
    else {
        while (1) {
            p -= factori_5(i);
            if (p == 0) {
                cout << i;
                break;
            }
            if (p < 0) {
                cout << -1;
                break;
            }
            i += 5;
        }
    }
    return 0;
}