#include <iostream>
#include <fstream>
using namespace std;
long p,n,i,ok,put,j,x;
int main()
{
	ifstream f("fact.in");
	ofstream g("fact.out");
	f>>p;
	if (p==0)
	{
		cout<<1;
		return 0;
	}
	i=0;
	ok=1;
	while (ok==1)
	{
		i++;
		put=0;
		for (j=1;j<=i;j++)
		{
			x=j;
			while (x%5==0)
			{
				put++;
				x/=5;
			}
		}
		if (put==p)
			ok=0;
	}
	g<<i;
	f.close();
	g.close();
	return 0;
}