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

if sum(W) % 2 != 0:
    print('impossible')
    exit()

target = sum(W) // 2
if max(W) > target:
    print('impossible')
    exit()

dp = [[False] * (target+1) for i in range(N+1)]
dp[0][0] = True

for i in range(N):
    for j in range(target+1):
        dp[i+1][j] |= dp[i][j]
        if j >= W[i]:
            dp[i+1][j] |= dp[i][j-W[i]]

print('possible' if dp[N][target] else 'impossible')