<?php
$n = trim(fgets(STDIN));
$w_array = explode(" ", trim(fgets(STDIN)));
rsort($w_array);
$w_target = array_sum($w_array);
if ( $w_target % 2 ) {
	echo 'impossible'.PHP_EOL;
	exit(0);
}
$w_target /= 2;

if ( ($w_array[0] == $w_target) || put_weight($w_array[0],1,1) ) {
	echo 'possible'.PHP_EOL;
}
else {
	echo 'impossible'.PHP_EOL;
}

function put_weight ( $put, $w_index, $w_count ) {
	global $w_array, $w_target, $n;
	if ( ($w_count >= $n) || ($w_index >= $n) ) {
		return FALSE;
	}
	if ( ($put + $w_array[$w_index]) > $w_target ) {
		return FALSE;
	}
	if ( ($put + $w_array[$w_index]) == $w_target ) {
		return TRUE;
	}
	$put += $w_array[$w_index];
	$ret = FALSE;
	for ( $i=$w_index+1; $i<$n; $i++ ) {
		$ret = put_weight($put, $i, $w_count+1);
		if ( $ret === TRUE ) {
			break;
		}
	}
	return $ret;
}