N = int(input())
W = list(map(int,input().split()))
S = sum(W)
if S % 2 == 1:
    print('impossible')
    exit()
DP = [0] * (S+1)
DP[0] = 1
for i in range(N):
    for k in range(S,-1,-1):
        if 0 <= k - W[i]:
            DP[k] |= DP[k-W[i]]
if DP[S//2]:
    print('possible')
else:
    print('impossible')