def dave(W,sumW,sumW2):
    if sumW2 < sumW/2:
        return False
    if sumW2 == sumW/2:
        return True
    for i in range(len(W)):
        if dave(W[1:],sumW,sumW2+W[0]):
            return True
    return False

def main():
    input()
    W=list(map(int, input().split()))
    sumW = sum(W)
    if sumW%2==1 :
        print("impossible")
        return 1
    W = sorted(W,reverse=True)
    if dave(W[1:],sumW,W[0]):
        print("possible")
    else:
        print("impossible")

main()