#include <fstream>

using namespace std;

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

    int p,pi=0,n=1,tmp;

    fin>>p;

    while(pi<p)
    {
        n++;
        tmp=n;
        while(tmp%5==0 && tmp!=0)
        {
            pi++;
            tmp=tmp/5;
        }
    }

    if(pi!=p) fout<<"-1";

    else fout<<n<<'\n';

    return 0;
}