#P1152F1. Neko Rules the Catniverse (Small Version)
Neko Rules the Catniverse (Small Version)
Description
This problem is same as the next one, but has smaller constraints.
Aki is playing a new video game. In the video game, he will control Neko, the giant cat, to fly between planets in the Catniverse.
There are $n$ planets in the Catniverse, numbered from $1$ to $n$. At the beginning of the game, Aki chooses the planet where Neko is initially located. Then Aki performs $k - 1$ moves, where in each move Neko is moved from the current planet $x$ to some other planet $y$ such that:
- Planet $y$ is not visited yet.
- $1 \leq y \leq x + m$ (where $m$ is a fixed constant given in the input)
This way, Neko will visit exactly $k$ different planets. Two ways of visiting planets are called different if there is some index $i$ such that the $i$-th planet visited in the first way is different from the $i$-th planet visited in the second way.
What is the total number of ways to visit $k$ planets this way? Since the answer can be quite large, print it modulo $10^9 + 7$.
The only line contains three integers $n$, $k$ and $m$ ($1 \le n \le 10^5$, $1 \le k \le \min(n, 12)$, $1 \le m \le 4$) — the number of planets in the Catniverse, the number of planets Neko needs to visit and the said constant $m$.
Print exactly one integer — the number of different ways Neko can visit exactly $k$ planets. Since the answer can be quite large, print it modulo $10^9 + 7$.
Input
The only line contains three integers $n$, $k$ and $m$ ($1 \le n \le 10^5$, $1 \le k \le \min(n, 12)$, $1 \le m \le 4$) — the number of planets in the Catniverse, the number of planets Neko needs to visit and the said constant $m$.
Output
Print exactly one integer — the number of different ways Neko can visit exactly $k$ planets. Since the answer can be quite large, print it modulo $10^9 + 7$.
Samples
3 3 1
4
4 2 1
9
5 5 4
120
100 1 2
100
Note
In the first example, there are $4$ ways Neko can visit all the planets:
- $1 \rightarrow 2 \rightarrow 3$
- $2 \rightarrow 3 \rightarrow 1$
- $3 \rightarrow 1 \rightarrow 2$
- $3 \rightarrow 2 \rightarrow 1$
In the second example, there are $9$ ways Neko can visit exactly $2$ planets:
- $1 \rightarrow 2$
- $2 \rightarrow 1$
- $2 \rightarrow 3$
- $3 \rightarrow 1$
- $3 \rightarrow 2$
- $3 \rightarrow 4$
- $4 \rightarrow 1$
- $4 \rightarrow 2$
- $4 \rightarrow 3$
In the third example, with $m = 4$, Neko can visit all the planets in any order, so there are $5! = 120$ ways Neko can visit all the planets.
In the fourth example, Neko only visit exactly $1$ planet (which is also the planet he initially located), and there are $100$ ways to choose the starting planet for Neko.