N = int(input())
W = list(map(int,input().split()))
S = sum(W)
if S % 2 == 1:
    print('impossible')
else:
    w_li = set([0])
    for i in W:
        w_li |= { i + w for w in w_li }
        if S/2 in w_li:
            print('possible')
            break
    else:
        print('impossible')