N = int(input())
W = list(map(int, input().split()))
full = sum(W)

if full % 2 == 1:
    print('impossible')
    exit()

dp = [-1 for i in range(full + 1)]
half = full // 2
dp[half] = 0

for i in range(N):
    for j in range(full):
        if dp[j] == i:
            if j + W[i] <= full:
                dp[j + W[i]] = i + 1
            if j - W[i] >= 0:
                dp[j - W[i]] = i + 1

print('possible' if dp[half] == N else 'impossible')