$ ssh -p 51197 picoplayer@saturn.picoctf.net
The authenticity of host '[saturn.picoctf.net]:51197 ([13.59.203.175]:51197)' can't be established.
ED25519 key fingerprint is SHA256:DiJcS90U9QussLS8HLR6l6BGJb5eCA0vRmA18IvDvw8.
This key is not known by any other names.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '[saturn.picoctf.net]:51197' (ED25519) to the list of known hosts.
picoplayer@saturn.picoctf.net's password:
Permission denied, please try again.
picoplayer@saturn.picoctf.net's password:
Welcome to Ubuntu 20.04.6 LTS (GNU/Linux 6.5.0-1023-aws x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

picoplayer@challenge:~$ ls
useless
picoplayer@challenge:~$ ./useless
Read the code first
picoplayer@challenge:~$ cat useless
#!/bin/bash
# Basic mathematical operations via command-line arguments

if [ $# != 3 ]
then
  echo "Read the code first"
else
        if [[ "$1" == "add" ]]
        then
          sum=$(( $2 + $3 ))
          echo "The Sum is: $sum"

        elif [[ "$1" == "sub" ]]
        then
          sub=$(( $2 - $3 ))
          echo "The Substract is: $sub"

        elif [[ "$1" == "div" ]]
        then
          div=$(( $2 / $3 ))
          echo "The quotient is: $div"

        elif [[ "$1" == "mul" ]]
        then
          mul=$(( $2 * $3 ))
          echo "The product is: $mul"

        else
          echo "Read the manual"

        fi
fi
picoplayer@challenge:~$ man useless

useless
     useless, -- This is a simple calculator script

SYNOPSIS
     useless, [add sub mul div] number1 number2

DESCRIPTION
     Use the useless, macro to make simple calulations like addition,subtraction,
     multiplication and division.

Examples
     ./useless add 1 2
       This will add 1 and 2 and return 3

     ./useless mul 2 3
       This will return 6 as a product of 2 and 3

     ./useless div 6 3
       This will return 2 as a quotient of 6 and 3

     ./useless sub 6 5
       This will return 1 as a remainder of substraction of 5 from 6

Authors
     This script was designed and developed by Cylab Africa

     picoCTF{us3l3ss_ch4ll3ng3_3xpl0it3d_8504}