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

SUM=sum(W)

if SUM%2!=0:
    print("impossible")
    exit()
    
X=SUM//2

DP=1
for w in W:
    DP=DP|(DP<<w)

if DP & (1<<X) != 0:
    print("possible")
else:
    print("impossible")