#include <fstream>
#include <math.h>
int f(int n) {return n/5+n/25+n/125+n/625+n/3125+n/15625+n/78125+n/390625 ;}
using namespace std;
int main()
{ifstream fin("fact.in");
ofstream fout("fact.out");
int n, p;
fin>>p;
if (p==0)
	fout<<"1"; 
else {
	int s=1;
	int e=2000000000;
	while (s+1<e)
	{int m=(s+e)/2 ;
	if (p<f(m)) 
		e=m-1;
	else s=m;
	}
fout<<s/5*5;
}
	return 0;
	
}