N=int(input())
W=sorted(list(map(int,input().split())))
S=0
T=""
P=0
for i in range(len(W)):
    S+=W[i]
if S % 2!=0:
    print("impossible")
else:
    S=int(S/2)
    for i in range(1,2**N):
        T=str(bin(i))[2:]
        M=0
        for j in range(len(T)):
            M+=int(T[j])*W[j]
        if M==S:
            P=1
    if P==0:
        print("impossible")
    else:
        print("possible")