N = int(input())
W = [int(i) for i in input().split()]

ans = "impossible"
for bits in range(1 << N):
    left = 0
    right = 0
    for i in range(N):
        if (bits >> i) & 1:
            left += W[i]
        else:
            right += W[i]
    if left == right:
        ans = "possible"
        break
print(ans)