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

if full % 2 == 1:
    print('impossible')
    exit()

dp = [[False for i in range(0, full * 2 + 1)] for j in range(N + 1)]
dp[0][full] = True


for i in range(N):
    for j in range(-full, full + 1):
        if dp[i][j]:
            dp[i + 1][j + W[i]] = True
            dp[i + 1][j - W[i]] = True
    
print('possible' if dp[N][full] else 'impossible')