a=int(input())
s=list(map(int,input().split()))
half_sum=sum(s)/2
if sum(s)%2==1:
    print("impossible")
else:
    half_sum=int(half_sum)
    r_list=[False]*(half_sum+1)
    r_list[0]=True
    for i in s:
        for j in range(half_sum,-1,-1):
            if r_list[j] and j+i<=half_sum:
                r_list[j+i]=True
    if r_list[half_sum]:
        print("possible")
    else:
        print("impossible")