N = int(input())
W = list(map(int, input().split()))
wsum = sum(W)
if wsum%2:
    print("impossible")
    exit()
s = set([0])
for i in range(N):
    ls = set()
    for ss in s:
        ls.add(ss+W[i])
        ls.add(ss)
    s = ls
if wsum//2 in s:
    print("possible")
else:
    print("impossible")