n=int(input())
w=[int(i) for i in input().split()]
a=[0]
new_a=set(a)
for i in w:
    for j in a:
        new_a.add(i+j)
    a=list(new_a)
if sum(w)%2==0 and sum(w)//2 in a:
    print("possible")
else:print("impossible")