#include <fstream>
using namespace std;

ifstream fin("fact.in");
ofstream fout ("fact.out");

int main ()
{
	int p,x1=0,x2=0,n=2,aux,max=1;
	fin >> p;
	if (p==1) {fout << 1;}
	else 
	while (max<p){
		aux=n;
		inceput2:
		if (n%2==0) { x1++; n=n/2; goto inceput2;}
		inceput5:
		if (n%5==0) { x2++; n=n/5; goto inceput5;}
		if (x1<x2) max=x1;
		else max=x2;
		if (x1==x2) max=x1;
		n=aux; n++; 	
	}
	fout << n-1;
	return 0;
}