if 중첩문 : elif

#!/bin/bash

echo -n "TYPE THE PACKAGE NAME YOU WANT TO INSTALL:"
read packname

echo -n "$packname will be installed, right? [Y/N]"
read answer

if [ $answer == y -o $answer == Y ] 
 then
   echo "Installing $packname ... "
   yum -y install $packname 
   
 elif [ $answer == n -o $answer == N ]
  then 
   echo "CANCELLED"
  else
   echo "PLEASE ANSWER WITH 'Y' OR 'N'"
 fi