N=int(input())
W=sorted(map(int,input().split()))
R={}
for x in W:
    S={}
    for k,v in R.items():
        S[R[k]+x]=R[k]+x
    R[x]=x
    R.update(S)

for k,v in R.items():
    if R[k]==sum(W)/2:
        print('possible')
        break
else:print('impossible')