n=int(input())
L=list(map(int,input().split()))
T=sum(L)
if T%2==1:exit(print("impossible"))
S={0}
for i in range(n):
    nx={0}
    for e in S:
        if e+L[i]<=T//2:
            nx.add(e+L[i])
    S=nx
print("possible" if T//2 in S else "impossible")