#include <fstream>

using namespace std;

int main()
{
    int n,p,q,q1;

    ifstream fin("fact.in");
    fin>>p;
    fin.close();

    if (p!=0)
    {
            n=0; q=q1=5;
        while(p>0)
        {
            while(q%5==0)
            {
                q=q/5;
                p--;
            }
            n+=5;
            q1+=5;
            q=q1;

        }

        ofstream fout("fact.out");
        if (p==0)
        fout<<n<<"\n";
        else fout<<"-1"<<"\n";
        fout.close();
        }
    else
        {
            ofstream fout("fact.out");
            fout<<'1';
            fout.close();
        }
    return 0;
}