N = int(input())
W = list(map(int , input().split()))

total = 0
for i in W:
  total += i

W.sort()

if total % 2 == 1:
  print("impossible")
else:
  total //= 2
  sum = [0 , W[0]]
  b = False
  for i in range(1 , N):
    sublist = []
    for s in sum:
      s += W[i]
      if s == total:
        b = True
        break
      elif not(s in sum) and s < total:
        sublist.append(s)
    if b:
      break
    sum += sublist
    sum.sort()
    
if b:
  print("possible")
else:
  print("impossible")