#include <iostream>
#include <fstream>
using namespace std;
int p,n,s1;
int t[14]={0,5,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125,244140625,1220703125};
int x[13]={0,6,31,156,781,3906,19531,97656,488281,2441406,12207031,61035156,305175781};
int det(int nr)
{
	int z=0;
	for(int i=1;i<=14;i++)
		if(nr/t[i]) z+=nr/t[i];
		else break;
	return z;
}
void caut(int s,int d)
{
	int m=(s+d)/2;
	int nr=det(m);
	if (s==d) n=m;
	else if(p>nr) caut(m+1,d);
		else caut(s,m);
}
int main()
{
	ifstream fin("fact.in");
	ofstream fout("fact.out");
	fin>>p;
	caut(1,1220703125);
	fout<<n;
	return 0;
}