#include <fstream>
using namespace std;
ifstream fin("factorial.in");
ofstream fout("factorial.out");
long long a,i,x,ci;
int main()
{
    fin>>a;
    if(a==0)
    {
        fout<<0;
        return 0;
    }
    while(x<a)
    {
        i=i+5; ci=i;
        while(ci%5==0)
            x++,ci=ci/5;
    }
    if(x>a)
        fout<<"-1";
    else
        fout<<i;
    return 0;
}