#include<stdio.h>
int f(int n){
	int x=0,i;
	while (n){
		x=n/5 + x;
		n/=5;}
	return x;
}
int main(){
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	int n=1,k,m,mij;
	scanf ("%d",&k);
	m=k*5;
	
	while (n!=m)
	{
		mij = (n+m)/2;
		if ( f(mij) >= k)
			m=mij;
		else
			n=mij+1;
	}
	if (f(n)==k)
		printf ("%d",n);
	else printf("-1");
	
	return 0;
}