#include <fstream>

using namespace std;

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

    int p;
    fin>>p;
    if (p==0)
        fout<<"1";
    else {
        int nr=0,copie,putere5=0;
        while(putere5 < p) {
            nr+=5;
            copie = nr;
            while(copie%5 == 0) {
                copie/=5;
                putere5++;
            }
        }
        if (putere5 > p) {
            fout<<"-1";
        }
        else fout<<nr;
    }




    fin.close();
    fout.close();
    return 0;
}