# your code goes here
#scale
N=int(input())
print(N)
W=[int(i) for i in input().split()]
print(W)
S=0
for i in range(N):
    S+=W[i]
if S%2==1:
    p="impossible"
else:
    W.sort()
    S//=2
    S-=W[-1]
    Nd=0
    if S==0:
        Nd=1
    else:
        W.pop(-1)
        T=[0]
        U=[0]
        i=0
        while Nd==0 and  i <N:
            print(T)
            T=U
            j=0
            print(T)
            while Nd==0 and j <len(T):
                v=T[j]+W[i]
                if v==S:
                    Nd=1
                else:
                    U.append(v)
                j+=1
            set(U)
    #                        print(j)
            i+=1
    if Nd==1:
        p="possible"
    else:
        p="impossible"
print(p)