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

def prtb(mat):#二次元matを整えて表示する
    print("------")
    for m in mat:
    	print(*m)
    print("------")

if sum(W)%2==1:
	print("impossible")
	exit()

M=sum(W)//2

dp=[[0 for j in range(M+1)] for i in range(N+1)]

dp[0][0]=1

for i in range(N):
	for j in range(M+1):
		if j+W[i]<=M:
			dp[i+1][j+W[i]]=max(dp[i+1][j+W[i]],dp[i][j])
		dp[i+1][j]=max(dp[i+1][j],dp[i][j])

#prtb(dp)
print("possible" if dp[-1][-1]==1 else "impossible")