N = int(input())
W = list(map(int, input().split(" ")))
S = sum(W)
if S % 2 == 1:
    print("impossible")
    exit(0)

dp = [False] * (S+1)
dp[0] = True
for j in range(N):
    nxt = [False] * (S+1)
    for i in range(S):
        if dp[i] :
            nxt[i+W[j]] = dp[i]
            nxt[i] = dp[i]
    nxt, dp = dp, nxt
print("impossible" if not dp[S//2] else "possible")