from collections import Counter

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

sm = sum(W)

if sm%2:
    print('impossible')
    exit()

cnt = Counter(W)
keys = sorted(cnt.keys())

dp = [[0]*(sm//2+1) for _ in range(len(keys)+1)]
for i in range(len(keys)+1):
    dp[i][0] = 1

for i in range(1,len(keys)+1):
    for s in range(sm//2+1):
        now = dp[i-1][s]
        k = min(s//keys[i-1],cnt[keys[i-1]])
        #print(keys[i-1],k)
        for j in range(1,k+1):
            now |= dp[i-1][s-j*keys[i-1]]
        dp[i][s] = now

for i in range(len(keys)+1):             
    if dp[i][sm//2]:
        print('possible')
        exit()
print('impossible')