#include <bits/stdc++.h>
//登録しよう！→ https://www.youtube.com/channel/UCRXsI3FL_kvaVL9zoolBfbQ
using namespace std;
using ll = long long;
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}//a,bの最大公約数(gcd)を求める
ll lcm(ll a,ll b){return abs(a*b)/gcd(a,b);}//a,bの最小公倍数(lcm)を求める
vector<ll> enum_div(ll n){vector<ll> ret;for(int i=1 ; i*i<=n ; i++){if(n%i == 0){ret.push_back(i);if(i!=1 && i*i!=n)ret.push_back(n/i);}}ret.push_back(n);return ret;}
//↑nの約数を求める
vector<bool> IsPrime; void sieve(size_t max){if(max+1 > IsPrime.size())IsPrime.resize(max+1,true);IsPrime[0] = false;IsPrime[1] = false;for(size_t i=2; i*i<=max; ++i)if(IsPrime[i])for(size_t j=2; i*j<=max; ++j)IsPrime[i*j] = false;}
//↑エラトステネスの篩で素数を求める
#define roundup(divisor,dividend) (divisor + (dividend - 1)) / dividend //切り上げ割り算
#define all(x) (x).begin(),(x).end() //xの初めから終わりまでのポインタ
#define size_t ll //size_tは自動でllに変換される
#define pb(x) push_back(x)
#define gre greater //sortを降順にする
#define pri_queue priority_queue //優先度付きキュー
#define syo(x) fixed << setprecision(x) //iostreamで小数をx桁表示
const ll MAX = 200000;
ll n,a,b;
const int mod = 1000000007;
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 >;
long long modpow(long long a, long long n, long long mod) {
    long long res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}
int main(){ //srand((unsigned)time(NULL));
  cin >> n >> a >> b;
  modint ans = modpow(2,n,mod)-1;
  modint x = 1;
  for (int i = 1; i <= a; i++) {
    x = (modint)x*(n-a+i)/(modint)i;
  }
  ans -= x;
  x = 1;
  for (int i = 1; i <= b; i++) {
    x = (modint)x*(n-b+i)/(modint)i;
  }
  ans -= x;
  cout << ans << endl;
}


Measured memory_bytes: 384