#include <fstream>
using namespace std;

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

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