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

sm = sum(W)
if sm%2 == 1:
    print('impossible')
    exit()
dp = [[True]+[False]*sm for _ in range(N)]
dp[0][W[0]] = True
for i in range(1, N):
    for j in range(sm+1):
        dp[i][j] = dp[i-1][j]
        if j - W[i] >= 0:
            dp[i][j] = dp[i-1][j-W[i]]
if dp[-1][sm//2]:
    print('possible')
else:
    print('impossible')