#include <iostream>
#include <fstream>
using namespace std;
int p,n;
int t[13]={0,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125,244140625,1220703125};
int x[13]={0,6,31,156,781,3906,19531,97656,488281,2441406,12207031,61035156,305175781};

int det()
{
	int i=0;
	while(p>x[i])
		i++;
	return i;
}
int main()
{
	int s,d;
	ifstream fin("fact.in");
	ofstream fout("fact.out");
	fin>>p;
	s=det()-1;
	n=t[s]+(p-x[s])*5;

	fout<<n;
	return 0;
}