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

for i in range(2**n):
  wr,wl=0,0
  for j in range(n):
    if i>>j&1:
      wr+=W[j]
    else:
      wl+=W[j]
  if wr==wl:
    print('possible')
    exit()
print('impossible')