import itertools

n = int(input())
weight_list = list(map(int, input().split()))
ans = False

weight_sum = sum(weight_list)
for i in range(1, n):
  for combination in list(itertools.combinations(weight_list, i)):
    if sum(combination) == weight_sum - sum(combination):
      ans = True
      break
    
# output
if ans:
  print('possible')
else:
  print('impossible')