# -*- coding: utf-8 -*-

n, = map(int, raw_input().split())
w = map(int, raw_input().split())

w = sorted(w)
w.reverse()

total = sum(w)
if total % 2 == 1:
    print 'impossible'
    exit()

half = total / 2
def is_pos(i, tmp):
    if tmp == half: return True
    if tmp > half: return False
    if i == len(w): return False
    return is_pos(i+1, tmp+w[i]) or is_pos(i+1, tmp)

print 'possible' if is_pos(0, 0) else 'impossible'