inpl = lambda: list(map(int,input().split()))
N = int(input())
W = inpl()
S = sum(W)
if S % 2:
    print('impossible')
    exit()
else:
    T = S//2
cur = {0}
for w in W:
    new = set()
    for c in cur:
        n = c + w
        if n == T:
            print('possible')
            exit()
        elif n < T:
            new.add(n)
    cur |= new
else:
    print('impossible')