#include<iostream>
#include<fstream>
using namespace std;
int main(void)
{
	fstream f,g;
	f.open("fact.in",ios::in);
	g.open("fact.out",ios::out);
	int n=1,i,imp1=25,pas=0, imp2=100;
	long long p=1;
	f>>p;
	if(p==0)
		g<<1;
	else
	{
		n=p*5;
		while(n>imp1)
		{
			pas++;
			imp1*=5;
		}
		n-=pas*5;
		pas=0;
		while(n>imp2)
		{
			pas++;
			imp2*=10;
		}
		n-=pas*5;
		g<<n;
	}
}