#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
#include<bitset>
#include<cassert>
#include<complex>
#include<fstream>
#include<cstdlib>
using namespace std;
typedef long long ll;
const int mod=1e9+7;
const int dx[]={1,0,0,-1},dy[]={0,1,-1,0};
int dp[100001];
int main(){
	int n,l;
	cin>>n>>l;
	dp[0]=1;
	int sum=1;
	for(int i=1;i<=n;i++){
		dp[i]=sum;
		(sum+=dp[i])%=mod;
		if(i>=l)
			(sum+=mod-dp[i-l])%=mod;
	}
	cout<<dp[n]<<endl;
}