#!python3

import itertools

def three_sum(listnum):
    
    possibility = itertools.combinations(listnum, 3)
    list_res = []

    for pos in possibility:
        sum = 0
        for num in pos:
            sum += num
        if sum == 0:
            list_res.append(pos)

    for i,l in enumerate(list_res):
        list_res[i] = tuple(sorted(l))
    list_res = set(tuple(list_res))

    for i in list_res:
        for j in i:
            print(str(j)+' ', end='')
        print()

print('----------------------------------------------')
three_sum([9, -6, -5, 9, 8, 3, -4, 8, 1, 7, -4, 9, -9, 1, 9, -9, 9, 4, -6, -8])
print('----------------------------------------------')
three_sum([4, 5, -1, -2, -7, 2, -5, -3, -7, -3, 1])
print('----------------------------------------------')
three_sum([-1, -6, -3, -7, 5, -8, 2, -8, 1])
print('----------------------------------------------')
three_sum([-5, -1, -4, 2, 9, -9, -6, -1, -7])