Concatenate an array with itself.sh

#Given a list of countries, each on a new line, your task is to read them into an array. Then, concatenate the array with itself (twice) - so that you have a total of three repetitions of the original array - and then display the entire concatenated array, with a space between each of the countries' names
arr=($(cat))
arr=("${arr[@]}" "${arr[@]}" "${arr[@]}")
echo ${arr[@]}