#include <fstream>
using namespace std;
int main()
{
    int P,N,t,k,i,j,p,nr;
ifstream f("fact.in");
ofstream g("fact.out");

    f>>P;
N=0;
if(P!=0)
{
    for(i=1;i<=P;i++)
{
    N=N+5;
}
t=N;
k=-1;
while(t/5>1)
{
    t=t/5;
    k=k+1;
}
N=N-5*k;

}
if(P==0) N=1;
p=1;
for(j=1;j<=N;j++)
{
    p=p*j;
}
while(p!=0)
{
    if(p%10==0)
    nr=nr+1;
}
if(nr!=P) g<<"-1";
else
g<<N;
g<<endl;
f.close();
g.close();


}