Powerful Ksenia

给 $n$ 个正整数 $a_i$,$1 \le a_i\le10^9$. 每次操作是选三个不同的下标 $i,j,k$ ，让 $a_i,a_j,a_k$ 都变成 $a_i \oplus a_j\oplus a_k$ 也就是这三个数的异或和. 让你判断是否能在 $n$ 次操作内，使这 $n$ 个正整数的值变成相同的. 若能，第一行输出YES，第二行输出 $m$ 表示操作数两，接下来 $m$ 行每行三个整数，描述一次操作； 若不能，输出NO.

Ksenia has an array $ a $ consisting of $ n $ positive integers $ a_1, a_2, \ldots, a_n $ . In one operation she can do the following: - choose three distinct indices $ i $ , $ j $ , $ k $ , and then - change all of $ a_i, a_j, a_k $ to $ a_i \oplus a_j \oplus a_k $ simultaneously, where $ \oplus $ denotes the [bitwise XOR operation](https://en.wikipedia.org/wiki/Bitwise_operation#XOR). She wants to make all $ a_i $ equal in at most $ n $ operations, or to determine that it is impossible to do so. She wouldn't ask for your help, but please, help her!

The first line contains one integer $ n $ ( $ 3 \leq n \leq 10^5 $ ) — the length of $ a $ . The second line contains $ n $ integers, $ a_1, a_2, \ldots, a_n $ ( $ 1 \leq a_i \leq 10^9 $ ) — elements of $ a $ .

Print YES or NO in the first line depending on whether it is possible to make all elements equal in at most $ n $ operations. If it is possible, print an integer $ m $ ( $ 0 \leq m \leq n $ ), which denotes the number of operations you do. In each of the next $ m $ lines, print three distinct integers $ i, j, k $ , representing one operation. If there are many such operation sequences possible, print any. Note that you do not have to minimize the number of operations.

5
4 2 1 7 2

YES
1
1 3 4

4
10 4 49 22

NO

In the first example, the array becomes $ [4 \oplus 1 \oplus 7, 2, 4 \oplus 1 \oplus 7, 4 \oplus 1 \oplus 7, 2] = [2, 2, 2, 2, 2] $ .