use strict;
use warnings;

my $num = <STDIN>;
my @w = split(' ', <STDIN>);

my $sum = eval join('+', @w);

my %p = (0 => 0);
my %n = %p;

my $ans = 'impossible';

if($sum%2 == 0){
  my $half = $sum/2;
  my $hs;

  LOOP: for my $i (@w){
    for my $j (keys %p){
      $hs = $j + $i;
      if($hs == $half){
        $ans = 'possible';
        last LOOP;
      }elsif($hs < $half){
        $n{$hs} = 1;
      }
    }
    %p = %n;
  }
}

print $ans;