N = int(input())

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

w = sum(W)


if w % 2 == 1:
    
    print('impossible')
    
    exit()
    
dp = [1] + [0] * w


for i in W:
    
    
    for j in range(w, i - 1, -1):
        
        dp[j] += dp[j - i]
        
if dp[w // 2]:
    
    print('possible')


else:
    
    print('impossible')