CF1138B Circus

**题意：** 有$n$组数（保证$n$是偶数），每组数中有两个数，第$i$组数中的数为$c_i$和$a_i$，其中$c_i,a_i$都为$0$或$1$ 您需要将$n$组数分成两部分，满足： - 每部分$\frac{n}{2}$组数。 - 第一部分中$c_i$的和=第二部分中$a_i$的和。 **数据范围：** $2\le n\le 5000$

The first line contains a single integer $ n $ ( $ 2 \le n \le 5\,000 $ , $ n $ is even) — the number of artists in the troupe. The second line contains $ n $ digits $ c_1 c_2 \ldots c_n $ , the $ i $ -th of which is equal to $ 1 $ if the $ i $ -th artist can perform as a clown, and $ 0 $ otherwise. The third line contains $ n $ digits $ a_1 a_2 \ldots a_n $ , the $ i $ -th of which is equal to $ 1 $ , if the $ i $ -th artist can perform as an acrobat, and $ 0 $ otherwise.

**样例1说明：** $c_1+c_4=1=a_2+a_3$，于是输出1 4.

In the first example, one of the possible divisions into two performances is as follows: in the first performance artists $ 1 $ and $ 4 $ should take part. Then the number of artists in the first performance who can perform as clowns is equal to $ 1 $ . And the number of artists in the second performance who can perform as acrobats is $ 1 $ as well. In the second example, the division is not possible. In the third example, one of the possible divisions is as follows: in the first performance artists $ 3 $ and $ 4 $ should take part. Then in the first performance there are $ 2 $ artists who can perform as clowns. And the number of artists in the second performance who can perform as acrobats is $ 2 $ as well.