n = int(input())
lst1 = list(map(int,input().split()))

def func(left,right,now):
    if now == n:
        return left==right
    if func(left+lst1[now],right,now+1):
        return True
    if func(left,right+lst1[now],now+1):
        return True

if func(0,0,0):
    print("possible")
else:
    print("impossible")