CF1395B.Boboniu Plays Chess

Boboniu likes playing chess with his employees. As we know, no employee can beat the boss in the chess game, so Boboniu has never lost in any round.

You are a new applicant for his company. Boboniu will test you with the following chess question:

Consider a $n\times m$ grid (rows are numbered from $1$ to $n$, and columns are numbered from $1$ to $m$). You have a chess piece, and it stands at some cell $(S_x,S_y)$ which is not on the border (i.e. $2 \le S_x \le n-1$ and $2 \le S_y \le m-1$).

From the cell $(x,y)$, you can move your chess piece to $(x,y')$ ($1\le y'\le m, y' \neq y$) or $(x',y)$ ($1\le x'\le n, x'\neq x$). In other words, the chess piece moves as a rook. From the cell, you can move to any cell on the same row or column.

Your goal is to visit each cell exactly once. Can you find a solution?

Note that cells on the path between two adjacent cells in your route are not counted as visited, and it is not required to return to the starting point.

鲍波牛喜欢和员工下棋。众所周知，没有任何员工能在国际象棋中击败老板，因此鲍波牛在任何一轮比赛中都从未输过。

你是一名该公司的新应聘者。鲍波牛将用下面这道国际象棋题目来测试你：

考虑一个 $n\times m$ 的网格（行编号从 $1$ 到 $n$，列编号从 $1$ 到 $m$）。你有一个棋子，初始位于某个非边界格子 $(S_x,S_y)$ 上（即满足 $2 \le S_x \le n-1$ 且 $2 \le S_y \le m-1$）。

从格子 $(x,y)$ 出发，你可以将棋子移动到 $(x,y')$（其中 $1\le y'\le m$，且 $y' \neq y$）或 $(x',y)$（其中 $1\le x'\le n$，且 $x'\neq x$）。换言之，该棋子的走法与“车”相同：即可以从当前格子移动到同一行或同一列上的任意其他格子。

你的目标是恰好访问每个格子一次。你能找到一个可行方案吗？

注意：在你路径中两个相邻位置之间的中间格子不视为被访问；此外，不要求最终返回起点。

The only line of the input contains four integers $n$, $m$, $S_x$ and $S_y$ ($3\le n,m\le 100$, $2 \le S_x \le n-1$, $2 \le S_y \le m-1$) — the number of rows, the number of columns, and the initial position of your chess piece, respectively.

输入仅有一行，包含四个整数 $n$、$m$、$S_x$ 和 $S_y$（$3\le n,m\le 100$，$2 \le S_x \le n-1$，$2 \le S_y \le m-1$），分别表示棋盘的行数、列数以及你的棋子的初始位置。

You should print $n\cdot m$ lines.

The $i$-th line should contain two integers $x_i$ and $y_i$ ($1 \leq x_i \leq n$, $1 \leq y_i \leq m$), denoting the $i$-th cell that you visited. You should print exactly $nm$ pairs $(x_i, y_i)$, they should cover all possible pairs $(x_i, y_i)$, such that $1 \leq x_i \leq n$, $1 \leq y_i \leq m$.

We can show that under these constraints there always exists a solution. If there are multiple answers, print any.

你需要输出 $n\cdot m$ 行。

第 $i$ 行应包含两个整数 $x_i$ 和 $y_i$（其中 $1 \leq x_i \leq n$，$1 \leq y_i \leq m$），表示你访问的第 $i$ 个格子。你必须恰好输出 $nm$ 个数对 $(x_i, y_i)$，且这些数对需覆盖所有满足 $1 \leq x_i \leq n$、$1 \leq y_i \leq m$ 的可能的数对 $(x_i, y_i)$。

在给定约束下，我们可证明解一定存在。若存在多个答案，输出任意一个即可。

Possible routes for two examples:

两个示例的可能路径：