#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int u,k,m,z;
long long p,s;
int main () {
	in>>k;
	p=1;u=2000000000;
	if(k==0){
		out<<1;
		return 0;
		
	}
	while(p<=u){
		m=(p+u)/2;
		s=0;z=5;
		while(z<=m){
			s=s+m/z;
			z=z*5;}
		if(s==k){
			while(m%5!=0)
				 m--;
			out<<m;
			break;}
		else
			if(k<s)
				u=m-1;
			else
				p=m+1;}
	if(p>u)
		out<<-1;
	return 0;
}