n = int(input())
values = list(map(int, input().split(' ')))

import functools
from collections import deque

total = functools.reduce(lambda x,y: x+y, values)

def yes(target):
    queue = deque()
    queue.appendleft((0,0))

    while 0 < len(queue):
        i, sum = queue.popleft()

        if sum == target:
            return True

        if i == n:
            return False

        queue.appendleft((i+1,sum))
        queue.appendleft((i+1,sum+values[i]))
        
    return False

if total%2 != 0:
    print('impossible')
else:
    print('possible' if yes(total/2) else 'impossible')