Equation - MarisaOJ: Marisa Online Judge

Equation

Time limit: 1000 ms
Memory limit: 256 MB
Find the number of positive integers solutions $(x_1, x_2,..., x_k)$ for the following equation: $$ \begin{equation} \begin{cases} x_1 < x_2 < ... < x_k \\\\ x_1 + x_2 + ... + x_k=n \end{cases} \end{equation} $$ ### Input - A single line contains two integers $n, k$. ### Output - Print the number of solutions, modulo $10^9+7$. ### Constraints - $1 \le n \le 10^9$. - $1 \le k \le 5$. ### Example Input: ``` 10 3 ``` Output: ``` 4 ```