N=int(input())
weights=list(map(int,input().split()))
S=sum(weights)
sum_list=set([0])
if S&1: 
  L.clear()
else:
  for weight in weights:
    sum_list |= set([weight + l  for l in sum_list])
    if S/2 in sum_list:
      break
print("possible" if S/2 in L else "impossible")