// 3乗解で， N <= 100 の全ケースと，given N <= 400 のときその N で想定解チェック
#include <cassert>
#include <iostream>
#include <vector>
#include <atcoder/modint>
using namespace std;

template <typename modint> struct acl_fac {
    std::vector<modint> facs, facinvs;
    acl_fac(int N) {
        assert(-1 <= N and N < modint::mod());
        facs.resize(N + 1, 1);
        for (int i = 1; i <= N; i++) facs[i] = facs[i - 1] * i;
        facinvs.assign(N + 1, facs.back().inv());
        for (int i = N; i > 0; i--) facinvs[i - 1] = facinvs[i] * i;
    }
    modint ncr(int n, int r) const {
        if (n < 0 or r < 0 or n < r) return 0;
        return facs[n] * facinvs[r] * facinvs[n - r];
    }
    modint operator[](int i) const { return facs[i]; }
    modint finv(int i) const { return facinvs[i]; }
};
using mint = atcoder::modint1000000007;
acl_fac<mint> fac(1000000);

mint solve(int N, int M) {
    acl_fac<mint> fac(N);
    vector<mint> ncrs(N + 1);
    for (int i = 0; i < int(ncrs.size()); i++) ncrs[i] = fac.ncr(N, i);
    vector<mint> ncr_cums(ncrs.size() + 1);
    for (int i = 0; i < int(ncrs.size()); i++) ncr_cums[i + 1] = ncr_cums[i] + ncrs[i];

    mint ret = 0;

    auto add_closed = [&](int l, int r) {
        // if (l > r) return;
        assert(l <= r + 1);
        l = max(l, 0);
        r = min(r, N);
        ret += ncr_cums[r + 1] - ncr_cums[l];
    };

    for (int h = 1; h <= N; h++) {
        if (M - (N - M) >= h) {
            add_closed(M, N);
        } else {
            int l = h + (N - h + 1) / 2;
            add_closed(l, N);
            if ((N - h) % 2) {
                add_closed(l, l - 1 + l - M);
            } else {
                add_closed(l + 1, l + l - M);
            }
        }
    }
    const int K = N - M;
    for (int h = 1; h <= K; h++) {
        const int l = h + (N - h + 1) / 2;
        if (l <= K) {
            add_closed(l, K);
            if ((N - h) % 2) {
                add_closed(l, N);
            } else {
                add_closed(l + 1, N);
            }
        } else {
            add_closed(h + N - K, N);
        }
    }
    for (int i = M; i <= N; i++) ret += fac.ncr(N, i) * N;
    return ret;
}


void validate_n3(int N) {
    vector dp(N + 1, vector<mint>(N + 1)); // dp[i][j] = 今終わったら ')' が i 個必要でここまで '(' を j 個使ったような場合の数
    vector sum(N + 1, vector<mint>(N + 1));
    dp[0][0] = 1;
    for (int t = 0; t < N; t++) {
        vector dpnxt(dp.size(), vector<mint>(dp[0].size()));
        vector sumnxt(dp.size(), vector<mint>(sum[0].size()));
        for (int i = 0; i < int(dp.size()); i++) {
            for (int j = 0; j < int(dp[i].size()); j++) {
                if (dp[i][j] == 0 and sum[i][j] == 0) continue;
                // ')' を使う場合
                dpnxt[max(0, i - 1)][j] += dp[i][j];
                sumnxt[max(0, i - 1)][j] += sum[i][j];
                if (!i) sumnxt[i][j] += dp[i][j];
                // '(' を使う場合
                dpnxt[i + 1][j + 1] += dp[i][j];
                sumnxt[i + 1][j + 1] += sum[i][j];
            }
        }
        dp = dpnxt;
        sum = sumnxt;
    }
    vector<mint> ret(N + 1);
    for (int i = 0; i < int(dp.size()); i++) {
        for (int j = 0; j < int(dp[i].size()); j++) {
            ret[j] += sum[i][j] + dp[i][j] * i;
        }
    }
    for (int i = 0; i <= N; i++) ret[i] += fac.ncr(N, i) * N;
    for (int i = int(ret.size()) - 1; i; i--) ret[i - 1] += ret[i];

    for (int m = 0; m <= N; m++) assert(solve(N, m) == ret[m]);
}

int main() {

    for (int n = 1; n <= 50; n++) validate_n3(n);

    int N, M;
    cin >> N >> M;
    if (N <= 400) validate_n3(N);
    cout << solve(N, M).val() << '\n';
}