from itertools import combinations

N = int(input())
array = [int(i) for i in input().split()]

def scale(array):
    _sum = sum(array)
    if _sum % 2 == 1:
        return 'impossible'
    else:
        for i in range(1, (N + 1) // 2):
            for ele in combinations(array, i):
                if _sum / 2 == sum(ele):
                     return 'possible'
        else:
            return 'impossible'

print(scale(array))