#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const ll MAX = 200001;
const ll MOD = 1000000007;

long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

template<class T,class U>
long long nCr(T n, U k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}


int main(void){
    COMinit();

    ll n,k,ans;

    cin >> n >> k;

    ans = 0;
    for(ll i=k-1; i<=n; i++){
        ans = (ans + (nCr(n, i)))%MOD;
        ans = (ans + (n-i))%MOD;
     }

    cout << ans << endl;


    return 0;
}