N = int(input())
w = list(map(int, input().split()))
if sum(w) % 2 != 0:
    print("impossible")
else:
    W = sum(w) // 2
    weight = set([0])
    w.sort()
    while len(w) > 0:
        crt_weight = w.pop()
        tmp_set = set()
        for i in weight:
            if i + crt_weight <= W:
                tmp_set.add(i + crt_weight)
        weight.update(tmp_set)
    if W in weight:
        print('possible')
    else:
        print('impossible')