N = int(input())
V = list(map(int, input().split()))

if sum(V) % 2:
    print("impossible")
else:
    total = int(sum(V) / 2)
    dp = [False] * (total+1)
    dp[0] = True

    for v in V:
        for t in reversed(range(v-1, total+1)):
            dp[t] |= dp[t - v]

    if dp[total]:
        print("possible")
    else:
        print("impossible")