#include <fstream>
using namespace std;

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

int nrz (unsigned long long n){
    unsigned long long i, nr = 0;
    for (i = 5;i <= n;i *= 5)
        nr += n/i;
    return nr;
}


int main(){
    long long p, i, n = 5, nr;
    fin >> p;
    if (p == 0){
        fout << 1;
        return 0;
    }
    nr = nrz(n);
    while (nr < p){
        n += 5;
        nr = nrz(n);
    }
    if (nr == p)
        fout << n;
    else fout << -1;
    fin.close();
    fout.close();
    return 0;
}