N = int(input())
W = list(map(int, input().split()))
S = sum(W)
if S % 2 != 0:
    print('impossible')
else:
    S = S // 2
    dp = [0] * (S + 1)
    dp[0] = 1
    for w in W:
        for i in range(S, w - 1, -1):
            dp[i] |= dp[i - w]
    print('possible' if dp[S] else 'impossible')