#![allow(unused_mut, non_snake_case,unused_imports)]
use std::iter;
use std::cmp::{max, min, Ordering};
use std::mem::{swap};
use std::collections::{HashMap,BTreeMap,HashSet,BTreeSet,BinaryHeap,VecDeque};
use std::iter::FromIterator;

//　高速 EOF要
//macro_rules! input {(source = $s:expr, $($r:tt)*) => {let mut iter = $s.split_whitespace();input_inner!{iter, $($r)*}};($($r:tt)*) => {let mut s = {use std::io::Read;let mut s = String::new();std::io::stdin().read_to_string(&mut s).unwrap();s};let mut iter = s.split_whitespace();input_inner!{iter, $($r)*}};}
//macro_rules! input_inner {($iter:expr) => {};($iter:expr, ) => {};($iter:expr, $var:ident : $t:tt $($r:tt)*) => {let $var = read_value!($iter, $t);input_inner!{$iter $($r)*}};}
//macro_rules! read_value {($iter:expr, ( $($t:tt),* )) => {( $(read_value!($iter, $t)),* )};($iter:expr, [ $t:tt ; $len:expr ]) => {(0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()};($iter:expr, chars) => {read_value!($iter, String).chars().collect::<Vec<char>>()};($iter:expr, usize1) => {read_value!($iter, usize) - 1};($iter:expr, $t:ty) => {$iter.next().unwrap().parse::<$t>().expect("Parse error")};}
// 低速 EOF不要
macro_rules! input {(source = $s:expr, $($r:tt)*) => {let mut iter = $s.split_whitespace();let mut next = || { iter.next().unwrap() };input_inner!{next, $($r)*}};($($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, ( $($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, $t:ty) => {$next().parse::<$t>().expect("Parse error")};}

/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */


static MOD: i64 = 1_000_000_007;
fn fact_init(MAX_N: usize) -> (Vec<i64>, Vec<i64>, Vec<i64>) {
    let mut Inv: Vec<i64> = vec![0; MAX_N];
    let mut fact: Vec<i64> = vec![0; MAX_N];
    let mut factInv: Vec<i64> = vec![0; MAX_N];

    Inv[1] = 1;
    for i in 2..MAX_N as i64 {
        Inv[i as usize] = Inv[(MOD % i) as usize] * (MOD - MOD / i) % MOD;
    }

    fact[0] = 1;
    fact[1] = 1;
    factInv[0] = 1;
    factInv[1] = 1;
    for i in 2..MAX_N as i64 {
        fact[i as usize] = (fact[(i - 1) as usize] * i) % MOD;
        factInv[i as usize] = (factInv[(i - 1) as usize] * Inv[i as usize]) % MOD;
    }
    (Inv, fact, factInv)

    //let (mut Inv,mut fact,mut factInv) = fact_init((N+1) as usize);
}

fn powmod(a: i64, b: i64,_MOD:i64) -> i64 {
    let mut a: i64 = a;
    let mut b: i64 = b;
    let mut res: i64 = 1;
    a %= _MOD;
    while b != 0 {
        if b % 2 == 1 {
            res = res * a % _MOD;
        }
        a = a * a % _MOD;
        b >>= 1;
    }
    res
}

fn inversemod(a: i64, _MOD: i64) -> i64 {
    powmod(a, _MOD - 2,_MOD)
}

fn nCr(n: usize, r: usize,_MOD:i64,fact:&Vec<i64>,factInv:&Vec<i64>) -> i64 {
    let mut ret :i64 = 0;
    if n >= r { ret = fact[n]*factInv[r]%_MOD*factInv[n-r]%_MOD; }
    ret
}
fn main(){
    input!(n:i64,k:i64);
    let (mut Inv,mut fact,mut factInv) = fact_init((10000) as usize);
    if n < k{
        println!("{}",0);
    }else{
        let mut n:i64 = n;
        let mut k:i64 = k;
        n-=k;
        let mut ans = nCr((n+k-1) as usize,(k-1) as usize, MOD,&fact,&factInv);;
        println!("{}",ans);
    }
}


Measured memory_bytes: 5036