//author:luckYrat(twitter:@luckYrat_)
//#include <bits/stdc++.h>

//def
#include <iostream>

#include <cmath>
#include <algorithm>
#include <iomanip>

//array
#include <vector>
#include <set>
#include <stack>
#include <queue>
#include <map>
#include <utility>
#include <climits>



using namespace std;

using ll = long long;
using P = pair<ll,ll>;

#define anyfill(n,s) setw(n) << setfill(s)
#define loop(s) for(int i = 0; s > i; i++)
#define rep(i,q) for(int i = 0; (q) > i; i++)
#define repp(i,n,q) for(int i = n; (q) > i; i++)
#define dep(i,q) for(int i = (q); 0 < i; i--)


#define MAX 1000000000
const long long mod = 1000000007;
#define EPS (1e-10)

#define pb push_back
#define fir first
#define scn second
#define ednl endl

#define YesNo(a) (a?"Yes":"No")
#define YESNO(a) (a?"YES":"NO")
#define yesno(a) (a?"yes":"no")


P ar[4] = {{0,1},{0,-1},{1,0},{-1,0}};
/*
確認ポイント
cout << fixed << setprecision(n) << 小数計算//n桁の小数表記になる
vector.unique()は隣接した同じ要素を削除するので先にソートをする

計算量は変わらないが楽できるシリーズ
C++11以降でmin({a,b,c...})で複数個のmic,maxを処理できる
min(max)_element(iter,iter)で一番小さい(大きい)値のポインタが帰ってくる
count(iter,iter,int)でintがiterからiterの間にいくつあったかを取得できる

*/

template< int mod >
struct ModInt {
  int x;

  ModInt() : x(0) {}

  ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

  ModInt &operator+=(const ModInt &p) {
    if((x += p.x) >= mod) x -= mod;
    return *this;
  }

  ModInt &operator-=(const ModInt &p) {
    if((x += mod - p.x) >= mod) x -= mod;
    return *this;
  }

  ModInt &operator*=(const ModInt &p) {
    x = (int) (1LL * x * p.x % mod);
    return *this;
  }

  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }

  ModInt operator-() const { return ModInt(-x); }

  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }

  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }

  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }

  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }

  bool operator==(const ModInt &p) const { return x == p.x; }

  bool operator!=(const ModInt &p) const { return x != p.x; }

  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while(b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }

  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(x);
    while(n > 0) {
      if(n & 1) ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }

  friend ostream &operator<<(ostream &os, const ModInt &p) {
    return os << p.x;
  }

  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt< mod >(t);
    return (is);
  }

  static int get_mod() { return mod; }
};

using modint = ModInt< mod >;



template< typename T >
T mod_pow(T x, T n, const T &p) {
  T ret = 1;
  while(n > 0) {
    if(n & 1) (ret *= x) %= p;
    (x *= x) %= p;
    n >>= 1;
  }
  return ret;
}
__attribute__((constructor))
void initial() {
 cin.tie(0);
 ios::sync_with_stdio(false);
}
int main(){
  long long n,a,b;cin>>n>>a>>b;
  modint z = (modint)(mod_pow(2LL,n,mod)-1);
  modint tmp = 1;
  for(int i = 1; a >= i; i++){
    tmp = (modint)tmp*(n-a+i)/(modint)i;
  }
  z -= tmp;
  tmp = 1;
  for(int i = 1; b >= i; i++){
    tmp = (modint)tmp*(n-b+i)/(modint)i;
  }
  cout << z-tmp << endl;
}

Measured memory_bytes: 256