#include <fstream>

using namespace std;
ifstream cin("factorial.in");
ofstream cout("factorial.out");

int nz (int n) {
    int r=0, f=5;
    while (f<=n) { 
        r+=n/f;
        f*=5;
    }
    return r;
}
long long n,p;
int main() {    
    cin >> p;
    if (p) {
        n = 5 * p;
        while (nz(n)>p)
            n -= 5;
        if (nz(n)<p) {
            cout << -1;
        } else {
            cout << n;
        }
    } else {
        cout << 1;
    }
    cin.close();
    cout.close();
    return 0;
}