#include<fstream.h>

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

main()
{long long N,P,i=0,p,a,b=-1;
f>>P;

if(P==0)
g<<'1';
else
{while(p>P)
{p=0;
N=5*(P-i);
a=N;
while(a>0)
{p=p+a/5;
a=a/5;}
i=i+1;}

if(p==P)
g<<N;

else
g<<b;}
}