#include<fstream>

using namespace std;

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

int main(){
	int n,p,gasit,c,i,m,j;
	in>>p;
	j=1000000000;
	i=p+1;
	gasit=0;
	while(i<=j && !gasit){
		m=(i+j)/2;
		c=0;
		n=m;
		while(n){
			c+=n/5;
			n/=5;
		}
		if(c==p)
			gasit=1;
		else
			if(p>c)
				i=m+1;
			else
				j=m-1;
	}
	if(gasit)
		m=m/5*5;
	if(m==0)
		m=1;
	if(!gasit)
		m=-1;
	out<<m;
	return 0;
}