N = int(input())
W = list(map(int,input().split()))
T = sum(W)
if T % 2 == 1:
    print("impossible")
    exit()
T2 = T // 2
Q = {0}
for w in W:
    Q2 = set()
    for q in Q:
        if q + w == T2:
            print("possible")
            exit()
        if q + w < T2:
            Q2.add(q + w)
    Q |= Q2
print("impossible")