#include <iostream>
#include <fstream>

using namespace std;

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

int Zero(long X)
{
    int number=0;
    int fives=5;

    while(fives<=X)
    {
        number+=X/fives;
        fives*=5;
    }
    return number;
}

long Fact(long P)
{
    if(P==0)
        return 1;
    else
    {
        int st=0;
        int dr=P*5;
        int result;

        while(st<=dr)
        {
            int mij=(st+dr)/2;

            if(Zero(mij)<=P)
            {
                result=mij;
                st=mij+5;
            }
            else
                dr=mij-5;
        }
        if(Zero(result)== P)
            return result - result%5;
        else
            return -1;
    }

}
int main()
{
    long P;
    cin>>P;
    cout<<Fact(P);
    return 0;
}