N = int(input())
V = list(map(int, input().split()))

if sum(V) % 2 == 1: print("impossible")
else:
    def sol(i, u):
        if i == N and u != 0: return 0
        if i == N and u == 0: return 1
        return max(sol(i + 1, u), sol(i + 1, u - V[i]))

    res = "possible" if sol(0, sum(V) // 2) == 1 else "impossible"
    print(res)