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