#!/usr/bin/env python3


def memoize(f):
    table = {}

    def func(*args):
        if args not in table:
            table[args] = f(*args)
        return table[args]
    return func


@memoize
def ok(weight, rest):
    if weight < 0:
        return False
    if weight == 0:
        return True
    for w in rest:
        r = list(rest)
        r.remove(w)
        if ok(weight - w, tuple(sorted(r))):
            return True
    return False

N = int(input())
W = [int(x) for x in input().split()]
if sum(W) % 2 == 1:
    print("impossible")
    exit()
if ok(sum(W) // 2, tuple(W)):
    print("possible")
else:
    print("impossible")