#include <fstream>
using namespace std;

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

int nr(int n)
{
	int nr=0;
	while(n){
		n/=5;
		nr+=n;
	}
	return nr;
}
 
int main(){
	int p;
	in>>p;
	if(p==0)
	{
		out<<1<<'\n';
		return 0;
	}
	int st=1,dr=1000000000;
	while(st<dr){
		int m=st+(dr-st)/2;
		if(nr(m)>=p)
		dr=m;
		else st=m+1;
	}
	if(nr(st)==p)
	out<<st<<'\n';
	else out<<-1<<'\n';

	in.close();
	out.close();
	return 0;
}