#include<fstream.h>
long n,m=0,i=0,aux;
int main()
{
ifstream f("fact.in");
ofstream g("fact.out");
f>>n;
while(n!=m)
 { i+=5; if( (i/5)%5 ) m++;
	 else {aux=i;
	       while (aux!=1)
		 {aux/=5;m++;}
	      }
}
if(m==0) g<<"1";
 else g<<i;
f.close();
g.close();
return 0;
}