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())

#print(keys)

dp = [[-1]*(sm//2+1) for _ in range(len(keys)+1)]
dp[0][0] = 0
for i in range(1,len(keys)+1):
    for s in range(sm//2+1):
        if dp[i-1][s] >= 0:#和sがi番目までで作れてるとき
            dp[i][s] = cnt[keys[i-1]]
        elif s-keys[i-1] >= 0 and dp[i][s-keys[i-1]] >= 1:
            dp[i][s] = dp[i][s-keys[i-1]] - 1
        else:
            dp[i][s] = -1

#print(dp)
print("possible" if dp[len(keys)][sm//2] >= 0 else "impossible")