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

if sum(ws) % 2 != 0:
    print('impossible')
elif W < max(ws):
    print('impossible')
else:
    psb_ws = set([0])
    ws.sort()
    while len(ws) > 0:
        w = ws.pop()
        tmp_set = set()
        for psb_w in psb_ws:
            if psb_w + w <= W:
                tmp_set.add(psb_w + w)
        psb_ws.update(tmp_set)
    if W in psb_ws:
        print('possible')
    else:
        print('impossible')