#[allow(unused_imports)]
use std::cmp::*;
#[allow(unused_imports)]
use std::collections::*;
use std::io::{BufWriter, Write};
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}
macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};
    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}
macro_rules! read_value {
    ($next:expr, [graph1; $len:expr]) => {{
        let mut g = vec![vec![]; $len];
        let ab = read_value!($next, [(usize1, usize1)]);
        for (a, b) in ab {
            g[a].push(b);
            g[b].push(a);
        }
        g
    }};
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };
    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };
    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };
    ($next:expr, usize1) => (read_value!($next, usize) - 1);
    ($next:expr, [ $t:tt ]) => {{
        let len = read_value!($next, usize);
        read_value!($next, [$t; len])
    }};
    ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error"));
}
#[allow(unused)]
macro_rules! debug {
    ($($format:tt)*) => (write!(std::io::stderr(), $($format)*).unwrap());
}
#[allow(unused)]
macro_rules! debugln {
    ($($format:tt)*) => (writeln!(std::io::stderr(), $($format)*).unwrap());
}

fn pow(a: i64, n: i64, m: i64) -> i64 {
    if n == 0 {
        return 1;
    }
    if n % 2 == 0 {
        let t = pow(a, n / 2, m);
        return t * t % m;
    }
    return a * pow(a, n - 1, m) % m;
}

fn ncr(n: i64, r: i64, fact: &mut Vec<i64>, factinv: &mut Vec<i64>, m: i64) -> i64 {
    return fact[n as usize] * factinv[r as usize] % m * factinv[(n - r) as usize] % m;
}

fn solve() {
    let out = std::io::stdout();
    let mut out = BufWriter::new(out.lock());
    macro_rules! puts {
        ($($format:tt)*) => (let _ = write!(out,$($format)*););
    }

    input! {
        n: i64,
        k: i64
    }

    let MOD = 1_000_000_007;

    let mut fact: Vec<i64> = vec![0; 202020];
    let mut factinv: Vec<i64> = vec![0; 202020];
    fact[0] = 1;
    factinv[0] = 1;
    for i in 1..202020 {
        fact[i] = fact[i - 1] * i as i64 % MOD;
        factinv[i] = pow(fact[i], MOD - 2, MOD);
    }

    let mut ans: i64 = 0;
    for i in 0..(min(k, n - 1) + 1) {
        ans +=
            ncr(n, i, &mut fact, &mut factinv, MOD) * ncr(n - 1, i, &mut fact, &mut factinv, MOD);
        ans %= MOD;
    }

    println!("{}", ans);
}
fn main() {
    // In order to avoid potential stack overflow, spawn a new thread.
    let stack_size = 104_857_600; // 100 MB
    let thd = std::thread::Builder::new().stack_size(stack_size);
    thd.spawn(|| solve()).unwrap().join().unwrap();
}


Measured memory_bytes: 12668