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

function getCombination($target, $nums = [], $full, $rest) {
    // if(count($nums) > 0) {
    //     echo "$target"."  "."{$nums[0]}".PHP_EOL;
    //     flush();
    // }
    if($full < $rest) {
        return false;
    }
    if(array_sum($nums) < $target) {
        return false;
    }
    if(count($nums) == 0) {
        return false;
    } else if($nums[0] == $target) {
        return true;
    } else if($target < $nums[0]) {
        return false;
    } else {
        if(getCombination($target-$nums[0], array_slice($nums,1), $full, $rest)) {
            return true;
        }
    }
    $rest += $nums[0];
    return getCombination($target, array_slice($nums, 1), $full, $rest);
}