#include<fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int p,mic, mare, mij;
int zero(int x)
{
int nr;
for(int i=5;i<=x;i*=5)
	nr+=x/i;
return nr;
}
int main()
{
in>>p;
mic=1;
mare=5*p;
mij=(mic+mare)/2;
while(mare>mic)
{
mij=mic+mare/2;
if(zero(mij)>=p)
	mare=mij-1;
else mic=mij+1;
}
if(zero(mic)==p)
	out<<mic<<'\n';
else out<<"-1\n";
in.close();
out.close();
return 0;	
}