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

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

def yes(i, sum, target):
    if n == i:
        return sum == target

    return yes(i+1, sum, target) or yes(i+1, sum+values[i], target)

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