import sys

n=int(input())
w=[int(i) for i in input().split()]

def dfs(index,weight):

    if weight<0:
        return

    if index==n:
        if weight==0:
            print("possible")
            sys.exit()
        return

    dfs(index+1,weight-w[index])
    dfs(index+1,weight)

weight=sum(w)
if weight%2!=0:
    print("impossible")
    sys.exit()
weight/=2
dfs(1,weight-w[0])
dfs(1,weight)

print("impossible")