#include<bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
int main() {
    int n, d; cin >> n >> d;
    vector<int> dp(n + 1, 0), sum(n + 2, 0);
    dp[0] = 1;
    sum[1] = 1;
    for (int i=1; i<=n; i++) {
        int l = max(0, i - d);
        dp[i] = (MOD + sum[i] - sum[l]) % MOD;
        sum[i + 1] = (sum[i] + dp[i]) % MOD;
    }
    cout << dp[n] << "\n";
}