from collections import defaultdict

_ = input()
w = list(map(int, input().split()))

dp = defaultdict(int)
dp[w.pop()] += 1
for i in range(len(w)):
  ndp = defaultdict(int)
  for x, v in dp.items():
  	ndp[x + w[i]] += v
  	ndp[x - w[i]] += v
  dp = ndp

if dp[0] > 0:
  print("possible")
else:
	print("impossible")