Okay, so i finally figured it out.
There was a phrase «For example, if six challenges until the end “Oozma Kappa” is forty points ahead, the audience at the stadium stands will just lose interest to the game.», which made me think that to "keep in suspense", on each step, i should choose such pair, that the current total sum is as close to zero as possible. However, this approach gives WA17. The proper approach is to keep, for as long as possible, such situation that if the first team gets all 6's for the remaining participants, and second gets all 0's, the first team wins; respectively, if 2nd team gets all 6's for the remaining participants, and 1st gets all 0's, 2nd team wins.
An example test:
11
5 5 5 5 5 5 6 6 6 6 6
6 6 6 6 6 6 0 0 0 0 0
Wrong WA17 approach gives
6 6 6 6 6 5 5 5 5 5 5
6 6 6 6 6 6 0 0 0 0 0
but last two rounds aren't interesting, because at that point 1st team has 50, and 2nd team has 36 points, and even if 2nd team gets all 6's for last two, and 1st all 0's, it's still 50:48 and 1st team wins.
One of the right answers is
5 5 5 5 5 5 6 6 6 6 6
6 6 6 6 6 6 0 0 0 0 0
Before last two rounds, we have 48:36, and 2nd team can potentially get all 6's on last two rounds for a draw 48:48; however, after a next round we have 54:36, and only then gets clear that 2nd team isn't going to win.

Cheers to Felix_Mate for a test and nice explanation.

> Which answer is correct for this test?
> My output (I also have WA17):
> 4 1
> 3 2
> 1 4
> 2 3
> Why is it wrong?

This answer is wrong. We understand that the first team is a winner after the third round:
4 1    ->    0 + (0-0) = 0
3 2    ->    0 + (5-2) = 3
1 4    ->    3 + (6-2) = 7 - we understand that the first team is a winner
2 3    ->    +(6-1) = 12

Correct answer is, for example:
4 2
3 4
2 3
1 1
Explanation - we understand that the first team is a winner only after the last (forth) round:
4 2    ->    0 + (0-2) = -2
3 4    ->    -2 + (5-2) = 1
2 3    ->    1 + (6-1) = 6 - we don't know who is a winner
1 1    ->    6 + (6-0) = 12

Edited by author 01.11.2018 02:24

Edited by author 01.11.2018 02:24