import itertools

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

weight_sum = sum(weight_list)

for bit in range(1 << n):
  we = 0
  for i in range(n):
    mask = 1 << i
    if bit & mask:
      we += weight_list[i]
  if we == weight_sum - we:
    ans = True
    break

# output
if ans:
  print('possible')
else:
  print('impossible')