#include <iostream>
#include<cmath>
using namespace std;

int F[510000] = { 1,1,2 };
int fun(int n, int m) {
	for (int i = 3; i <= m; i++) {
		F[i] = 1 << (i - 1);
	}
	for (int i = 3; i <= n; i++) {
		if (i <= m) {
			continue; 
		}
		F[i] = 2 * F[i - 1] - F[i - m - 1];
	}	
	return F[n]%10007;
}
int main()
{
	int n,m;
	cin >> n>>m;
	if (m == 1)
		cout<<1%10007;
	else
		cout << fun(n, m);
	return 0;
}
 

注：商湯筆試題，只能通過50%。

參考：

https://88250.b3log.org/steps-problem.html