#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
    int n,l;
    cin>>n>>l;
    const ll mod=1e9+7;
    ll dp[n+1];
    dp[0]=1;
    dp[1]=1;
    for(int i=2;i<=n;i++){
	    dp[i]=0;
        for(int j=1;j<=l;j++){
            if(i-j<0)break;
            dp[i]+=dp[i-j];
            dp[i]%=mod;
        }
    }
    cout<<dp[n]<<endl;
}