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#7178. 主教

统计

国际象棋中的象会攻击所有与它在同一对角线上的方格。 在 $n \times m$ 的棋盘上放置尽可能多的象,使得它们互不攻击。

输入格式

第一行包含两个整数 $n$ 和 $m$:棋盘的尺寸 ($1 \le n, m \le 10^5 + 1$)。

输出格式

第一行输出一个整数 $k$:在 $n \times m$ 的棋盘上互不攻击的象的最大数量。接下来的 $k$ 行,每行输出两个整数:象的坐标。第一个坐标应在 $[1, n]$ 范围内,第二个坐标应在 $[1, m]$ 范围内。如果存在多种可能的答案,输出其中任意一种即可。

样例

输入 1

2 5

输出 1

6
2 5
1 5
2 3
1 1
1 3
2 1

输入 2

5 5

输出 2

8
1 1
1 2
5 4
1 3
5 3
1 4
5 2
1 5

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