CF1552E.Colors and Intervals

The numbers $1, \, 2, \, \dots, \, n \cdot k$ are colored with $n$ colors. These colors are indexed by $1, \, 2, \, \dots, \, n$. For each $1 \le i \le n$, there are exactly $k$ numbers colored with color $i$.

Let $[a, \, b]$ denote the interval of integers between $a$ and $b$ inclusive, that is, the set ${a, \, a + 1, \, \dots, \, b}$. You must choose $n$ intervals $[a_1, \, b_1], \, [a_2, \, b_2], \, \dots, [a_n, \, b_n]$ such that:

• for each $1 \le i \le n$, it holds $1 \le a_i \lt b_i \le n \cdot k$;
• for each $1 \le i \le n$, the numbers $a_i$ and $b_i$ are colored with color $i$;
• each number $1 \le x \le n \cdot k$ belongs to at most $\left\lceil \frac{n}{k - 1} \right\rceil$ intervals.

One can show that such a family of intervals always exists under the given constraints.

数字 $1, \, 2, \, \dots, \, n \cdot k$ 被用 $n$ 种颜色染色。这些颜色编号为 $1, \, 2, \, \dots, \, n$。对每个 $1 \le i \le n$，恰好有 $k$ 个数被染成颜色 $i$。

记 $[a, \, b]$ 为从 $a$ 到 $b$（含端点）的所有整数构成的区间，即集合 $\{a, \, a + 1, \, \dots, \, b\}$。你需要选出 $n$ 个区间 $[a_1, \, b_1], \, [a_2, \, b_2], \, \dots, [a_n, \, b_n]$，满足：

• 对每个 $1 \le i \le n$，均有 $1 \le a_i \lt b_i \le n \cdot k$；
• 对每个 $1 \le i \le n$，数 $a_i$ 和 $b_i$ 均被染成颜色 $i$；
• 每个数 $1 \le x \le n \cdot k$ 至多属于 $\left\lceil \frac{n}{k - 1} \right\rceil$ 个区间。

可以证明：在给定约束条件下，这样的区间族总存在。

The first line contains two integers $n$ and $k$ ($1 \le n \le 100$, $2 \le k \le 100$) — the number of colors and the number of occurrences of each color.

The second line contains $n \cdot k$ integers $c_1, \, c_2, \, \dots, \, c_{nk}$ ($1 \le c_j \le n$), where $c_j$ is the color of number $j$. It is guaranteed that, for each $1 \le i \le n$, it holds $c_j = i$ for exactly $k$ distinct indices $j$.

第一行包含两个整数 $n$ 和 $k$（$1 \le n \le 100$，$2 \le k \le 100$）—— 分别表示颜色种类数和每种颜色出现的次数。

第二行包含 $n \cdot k$ 个整数 $c_1, \, c_2, \, \dots, \, c_{nk}$（$1 \le c_j \le n$），其中 $c_j$ 表示编号为 $j$ 的数字的颜色。保证对于每个 $1 \le i \le n$，恰好存在 $k$ 个不同的下标 $j$ 满足 $c_j = i$。

Output $n$ lines. The $i$-th line should contain the two integers $a_i$ and $b_i$.

If there are multiple valid choices of the intervals, output any.

输出 $n$ 行。第 $i$ 行应包含两个整数 $a_i$ 和 $b_i$。

如果存在多个满足条件的区间选择方案，输出任意一个即可。

In the first sample, each number can be contained in at most $\left\lceil \frac{4}{3 - 1} \right\rceil = 2$ intervals. The output is described by the following picture:

In the second sample, the only interval to be chosen is forced to be $[1, \, 2]$, and each number is indeed contained in at most $\left\lceil \frac{1}{2 - 1} \right\rceil = 1$ interval.

In the third sample, each number can be contained in at most $\left\lceil \frac{3}{3 - 1} \right\rceil = 2$ intervals. The output is described by the following picture:

在第一个样例中，每个数最多可被 $\left\lceil \frac{4}{3 - 1} \right\rceil = 2$ 个区间包含。输出由下图描述：

在第二个样例中，唯一可选的区间被迫为 $[1, \, 2]$，且每个数确实最多被 $\left\lceil \frac{1}{2 - 1} \right\rceil = 1$ 个区间包含。

在第三个样例中，每个数最多可被 $\left\lceil \frac{3}{3 - 1} \right\rceil = 2$ 个区间包含。输出由下图描述：