<?php
$num = trim(fgets(STDIN));
$nums = explode(" ", trim(fgets(STDIN)));
$sum = array_sum($nums);
if($sum%2 == 0) {
    $halfSum = $sum/2;
    rsort($nums);
    echo getCombination($halfSum, $nums)?"possible":"impossible";
} else {
    echo "impossible";
}
echo PHP_EOL;

function getCombination($target, $nums = []) {
    if(count($nums) == 0) {
        return false;
    } else if($nums[0] == $target) {
        return true;
    }
    if($target > $nums[0]) {
        if(getCombination($target-$nums[0], array_slice($nums,1))) {
            return true;
        }
    }
        return getCombination($target, array_slice($nums, 1));
}