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

sum_W=sum(W)
if sum_W%2==1:
    print("impossible")
    exit()

target=sum_W//2
box=set([0])
for w in W:
    n_box=set()
    for b in box:
        if b+w<=target:
            n_box.add(b+w)
    box|=n_box
    if target in box:
        print("possible")
        exit()

print("impossible")