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

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

if sum % 2:   #0以外はTrue
  print("impossible")
else:
  bit_dp = 1
  for i in W:
    bit_dp = bit_dp | bit_dp << i
  if bit_dp & 1 << sum // 2:
    print("possible")
  else:
    print("impossible")