def search(N, ws, Sum): q = [Sum] s = [0] res = False while q: target = q.pop(0) start = s.pop(0) for i in range(start, N): d = target - ws[i] if d == 0: res = True q.clear() break elif d < 0: continue elif d > 0: q_ = [target - ws[j] for j in range(i, N)] q.extend(q_) s_ = [j for j in range(i+1, N+1)] s.extend(s_) # print(q) break return res def main(): N = int(input()) ws = list(map(int, input().split())) ws.sort() ws.reverse() ws_sum = sum(ws) if ws_sum % 2 == 0: Sum = ws_sum // 2 res = search(N, ws, Sum) else: res = False print(ws_sum / 2) if res: print('possible') else: print('impossible') main()