N = int(input())
w = list(map(int, input().split()))
W = 0
for i in w:
    W += i / 2
if W == int(W):
    W = int(W)
    p = [False] * (W + 1)
    p[0] = True
    for i in w:
        for k in range(len(p)-1, -1, -1):
            if p[k] and k + i <= W:
                p[k+i] = True
    if p[W]:
        print("possible")
    else:
        print("impossible")
else:
    print("impossible")