n = int(input())
w = list(map(int, input().split()))

if sum(w) % 2:
    print('impossible')
else:
    t = 10 ** 4 + 10
    dp = [[False] * t for _ in range(n + 1)]
    # dp[i][j] := i番目までの重りでjを作れるかどうか
    dp[0][0] = True
    for i in range(n):
        for j in range(t):
            if j - w[i] >= 0:
                dp[i + 1][j] |= dp[i][j - w[i]]
            dp[i + 1][j] |= dp[i][j]
    
    print('possible') if dp[-1][sum(w) // 2] else print('impossible')