N=int(input())
W=list(map(int,input().split()))
if sum(W)%2==1:
    print("impossible")
    exit()
SUM=1
for i in range(N):
    SUM=SUM | SUM<<W[i]
SUM=str(bin(SUM))
SUM=SUM[::-1]
#print(SUM)
if SUM[N//1]=="1":
    print("possible")
else:
    print("impossible")