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