Count the number of non-negative solutions to the following inequality:
$$x_1 + x_2 + ... + x_k \le n$$
### Input
- A single line containing two integers $n, k$.
### Output
- Print the number of solutions modulo $10^9 + 7$.
### Constraints
- $1 \le n,k \le 10^6$.
### Sample test
Input
```
2 3
```
Output:
```
10
```
