def solve(data):
    dp = [False] * 100000
    dp[0] = True
    if sum(data) % 2 != 0:
        return False

    total = sum(data) / 2

    for v in data:
        for t in xrange(total, v - 1, -1):
            dp[t] |= dp[t - v]

    return dp[total]


N = int(raw_input())
data = map(int, raw_input().split(" "))

print "possible" if solve(data) else "impossible"