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

total_w = sum(W)
if total_w % 2 == 1:
    print("impossible")
    exit(0)

setw = set([0])

for w in W:
    new_setw = set(setw) # cannot change set size inside loop
    for v in setw:
        nv = v + w
        if nv == total_w//2:
            print("possible")
            exit(0)
        if nv < total_w//2:
            new_setw.add(nv)
    setw = new_setw

print("impossible")