n = int(input()) w = list(map(int, input().split())) dp = [False for i in range(10001)] dp[0] = True for i in range(n): for j in range(10000,-1,-1): if dp[j] and j + w[i] <= 10000: dp[j + w[i]] = True for i in range(10001): if dp[i] and i*2 == sum(w): print("possible") exit() print("impossible")