NUMBER=14
    
    user_input=
    until [[ "$user_input" =~ ^[+-]?[0-9]+$ ]] && ( [ $user_input -eq $NUMBER ] || [ $user_input -eq $(($NUMBER * -1)) ] ); do
        read -p "input either $NUMBER or $(($NUMBER * -1)): " user_input
    done
    echo "user input:  $user_input"