Problem Statement

You are given strings $X$ and $Y$ of length $N$ consisting of A and B. Let $X_i$ denote the $i$-th character of $X$.

Determine whether it is possible to make $X$ equal to $Y$ by performing the following operation between $0$ and $\left\lfloor \frac{N}{2} \right\rfloor$ times, inclusive.

• Choose a pair of integers $(l, r)$ such that $1\leq l < r \leq N$, $X_l=$ A, and $X_r=$ B. Reverse the elements of $X$ from the $l$-th to the $r$-th position. Here, "reversing the elements of $X$ from the $l$-th to the $r$-th position" means simultaneously replacing $X_l,X_{l+1},\ldots,X_{r-1},X_r$ with $X_r,X_{r-1},\ldots,X_{l+1},X_l$.

If it is possible to make $X$ equal to $Y$, output one such sequence of operations.

$T$ test cases are given; solve each of them.

Constraints

• $1 \leq T \leq 2.5\times 10^5$
• $2 \leq N \leq 5\times 10^5$
• The sum of $N$ over all test cases is at most $5\times 10^5$.
• $X$ and $Y$ are strings of length $N$ consisting of A and B.
• All input values are integers.

Input

The input is given from Standard Input in the following format:

T
\mathrm{case}_1
\mathrm{case}_2
\vdots
\mathrm{case}_T

Each test case is given in the following format:

N
X
Y

Output

Output the answers for $\mathrm{case}_1,\mathrm{case}_2,\ldots,\mathrm{case}_T$ in this order in the following format.

If it is impossible to make $X$ equal to $Y$ using between $0$ and $\left\lfloor \frac{N}{2} \right\rfloor$ operations, inclusive, output No.

If it is possible, output a sequence of operations in the following format:

Yes
K
l_1 r_1
l_2 r_2
\vdots
l_K r_K

Here $K$ is the number of operations, and $l_i, r_i$ are the integers $l, r$ chosen in the $i$-th operation. These must satisfy the following:

• $0 \leq K \leq \left\lfloor \frac{N}{2} \right\rfloor$
• $1 \leq l_i < r_i \leq N$

If there are multiple valid sequences of operations, any of them will be accepted.