#include <fstream>
#define ll long long
using namespace std;

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


ll result(int p) {
    
    if(p == 0)
        return 1;
    for(ll i = 5, d = 0; ; i *= 5, ++d) {

        ll a, b;
        a = i / 5 + d;
        b = i + (d + 1);

        if(p >= a && p < b - (d+1)) {
            return 5 * (p - d);
        }
        else if(p >= b - (d+1) && p < b)
            return -1;
    }
    return -1;
}


int main() {

    int p;
    in >> p;
    out << result(p);

    return 0;
}