Bash Script - check argument in array

#create an array
arr=(1 2 3 4 5 6)
#declare variable "rn" and random select a nuber
declare -i rn=$RANDOM*${#arr[@]}/32767echo "
rn = $rn"
#print all arguments in array
echo "array : ${arr[@]}"
#check if rn in array
for i in ${arr[@]}
   do  
       if [ "$i" = "$rn" ]; then        
            echo "HI!!"   
       fi
done
echo "==ending=="