#include <fstream>
using namespace std;
 
long fact(long a);
 
int main()
{
    long a;
    ifstream in("fact.in");
    in>>a;
    in.close();
    ofstream out("fact.out");
    out<<fact(a)<<"\n";
    out.close();
    return 0;
}
 
 
long fact(long a)
{  
    if (a==0) return 1;
	long sum=a*5;
	long nr=25;
	while (sum>=nr)
	{
		sum-=5*((sum-1)/nr);
		nr*=5;
	}
	return sum;
}