#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long long p,i=1,nr,v[]={0,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125},sum;
int main ()
{
	f>>p;
	if (p==0)
		g<<"1";
	else if (p<5 && p>0)
		g<<p*5;
	else
	{
		nr=p*5;
		while (v[i]<=nr)
		{
			sum=v[i];
			while (sum<nr)
			{
				sum+=v[i];
				nr-=5;
			}
			i++;
		}
		g<<nr;
	}
	return 0;
}