#include<fstream.h>
unsigned long int x,p;
int i,j,k,l;
int main ()
{ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
while (i+j<p)
	{i++;
	if(i%5==0)
		j=j+i/5;
	}
if (i+j==p)
	g<<i*5;
else
	g<<0;
f.close();
g.close();
return 0;
}