#include<fstream>
using namespace std;

unsigned long long int p, i, nr;
int k;

int main()
{
ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
f.close();
if(p<0)
	g<<-1;
else if(p==0)
	g<<-1;
else
{i=1;
while(p>=61035156)
{p-=61035156; nr+=48828125;}
while(p>=12207031)
{p-=12207031; nr+=9765625;}
while(p>=2441406)
{p-=2441406; nr+=1953125;}
while(p>=488281)
{p-=488281; nr+=390625;}
while(p>=97656)
{p-=97656; nr+=78125;}
while(p>=19531)
{p-=19531; nr+=15625;}
while(p>=3906)
{p-=3906; nr+=3125;}
while(p>=781)
{p-=781; nr+=625;}
while(p>=156)
{p-=156; nr+=125;}
while(p>=31)
{p-=31; nr+=25;}
while(p>=6)
{p-=6; nr+=5;}
nr+=p;
g<<nr*5;
}
g.close();
return 0;
}