#include <fstream>

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

int main()
{
    int p,aux;
    bool ok = false;
    fin>>p;
    aux = p;
    if(p==0) fout<<"1\n";
    else
    {
        if(aux%5==0)
        {
        while(aux%5==0)
            aux/=5;
        if(aux==1)
        {
            fout<<"-1\n";
            ok = true;
        }
        }
        if(ok==true);
        else if(p<5) fout<<p*5<<"\n";
        else if(p<25) fout<<(p-1)*5<<"\n";
        else if(p<125) fout<<(p-2)*5<<"\n";
        else if(p<625) fout<<(p-3)*5<<"\n";
        else if(p<3125) fout<<(p-4)*5<<"\n";
        else if(p<15625) fout<<(p-5)*5<<"\n";
        else if(p<78125) fout<<(p-6)*5<<"\n";
        else if(p<390625) fout<<(p-7)*5<<"\n";
        else if(p<1953125) fout<<(p-8)*5<<"\n";
        else if(p<9765625) fout<<(p-9)*5<<"\n";
        else if(p<48828125) fout<<(p-10)*5<<"\n";
        else if(p<244140625) fout<<(p-11)*5<<"\n";
    }



    fout.close();
    return 0;
}