import java.util.Scanner;

public class test {
public static void main(String[] args) {
Scanner sc =new Scanner(System.in);
int n = sc.nextInt();
int res,yushu,res6=0,m;
while (n>0){
if (n%8==0){
res=n/8;
System.out.println(res);
return;
} else {
yushu = n % 8;
res = n / 8;
if(yushu % 6 == 0){
res6 =yushu/6;
}else {
while (yushu % 6 != 0){
m=n-(res-1)*8;
yushu = m % 6;
res=res-1;
if(res<1){
System.out.println(-1);
return;
}
res6=m/6;
}
}
System.out.println(res+res6);
return;
}
}
}
}