import math, sequtils, strutils

let
  _ = readLine stdin
  ws = stdin.readLine.split.map parseInt
  s = sum ws
  h = s div 2

if s mod 2 != 0:
  echo "impossible"
else:
  var dp = false.repeat h.succ
  dp[0] = true

  for w in ws:
    for i in countdown(h, 0):
      if not dp[i] or w + i > h:
        continue

      dp[w + i] = true

  if dp[h]:
    echo "possible"
  else:
    echo "impossible"