N = int(input())
W = list(map(int,input().split()))
w = int(sum(W)/2)

def ballance(i):
    weight = 0
    wsum = [0]*N
    wlist = [0]*N
    while True:
        while weight < w and i < N:
            weight += W[i]
            wsum[i] = weight
            wlist[N-i-1] = 1
            i += 1
        if weight == w:
            return 'possible'
        elif wlist.count(2) != N and i < N:
            wlist[N-i] = 0
            i = wlist.index(1)
            weight = wsum[i]
            wlist[i] = 2
            i += 1
        else:
            break
    return 'impossible'

if w*2 != sum(W):
    print('impossible')
else:
    print(ballance(0))