#include<fstream>
#include<iostream>
using namespace std;
int main()
{
	int n,p,n5=0;
	ifstream fin("factorial.in");
	fin>>p;
	while(n5!=p)
		for(n=1;;n++)
			while(n%5==0)
		    {
				n5++;
			}
	ofstream fout("factorial.out");
	fout<<n;
	return 0;
}