<?php
$n = trim(fgets(STDIN));
$vList = explode(' ', (trim(fgets(STDIN))));
$sum = array_sum($vList);
rsort($vList);
$a = 0;
$b = 0;

if(!$sum%2) {
	echo 'impossible'.PHP_EOL;	
}
foreach($vList as $v) {
	if($a > $b) {
		$b = $b + $v;
	} else {
		$a = $a + $v;
	}
}
if($a === $b) {
	echo 'possible'.PHP_EOL;
} else {
	echo 'impossible'.PHP_EOL;
}