import itertools

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

x = list(itertools.permutations(w))
c = False

if sum(w) % 2 != 0:
    print('impossible')
else:
    b = sum(w) // 2
    for var in x:
        a = 0
        for i in var:
            a += i
            if a == b:
                c = True
                break
            elif a > b:
                break
    if c:
        print('possible')
    else:
        print('impossible')