맥으로 터미널을 이용해서 서버 접속하려고 하는데 이런 오류가 뜨네요.

unguui-MacBook-Pro:~ sungulee$ sudo chmod 400/Users/sungulee/Desktop/KEY/iiiiamsam_mykey.pem 

usage: chmod [-fhv] [-R [-H | -L | -P]] [-a | +a | =a [i][# [ n]]] mode|entry file ...

chmod [-fhv] [-R [-H | -L | -P]] [-E | -C | -N | -i | -I] file ...

Sunguui-MacBook-Pro:~ sungulee$ ssh -i /Users/sungulee/Desktop/KEY/iiiiamsam_mykey.pem ubuntu@52.78.228.232

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

@     WARNING: UNPROTECTED PRIVATE KEY FILE!     @

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

Permissions 0644 for '/Users/sungulee/Desktop/KEY/iiiiamsam_mykey.pem' are too open.

It is required that your private key files are NOT accessible by others.

This private key will be ignored.

Load key "/Users/sungulee/Desktop/KEY/iiiiamsam_mykey.pem": bad permissions

ubuntu@52.78.228.232: Permission denied (publickey).

Sunguui-MacBook-Pro:~ sungulee$