#include <bits/stdc++.h>
#include <cassert>
typedef long long int ll;
using namespace std;

// @@ !! LIM(mod f:power)
// --> f:gcd f:intDiv mod f:power
// ---- inserted function gcd from util.cc
// g = eGCD(a, b, s, t)  --->  sa + tb = g
ll eGCD(ll a, ll b, ll& s, ll& t) {
  if (a == 0) {
    s = 0;
    t = 1;
    return b;
  }
  ll u = 0;
  ll g = eGCD(b % a, a, t, u);
  s = u - (b / a) * t;
  return g;
}

// gcd(0, x) = x, gcd(-x, y) = gcd(x, y)
ll gcd(ll a, ll b) {
  ll dummy1 = 0;
  ll dummy2 = 0;
  return eGCD(abs(a), abs(b), dummy1, dummy2);
}
// ---- end gcd
// ---- inserted function intDiv from util.cc
// imod, divFloor, divCeil

// imod(x, y) : remainder of x for y
// for y > 0:
//   imod(x, y)  = r where x = dy + r, 0 <= r < y
//   imod(x, -y) = r where x = dy + r, 0 >= r > y
// Thus, imod( 10,  7) =  3
//       imod(-10,  7) =  4
//       imod( 10, -7) = -4
//       imod(-10, -7) = -3
ll imod(ll x, ll y) {
  ll v = x % y;
  if ((x >= 0) == (y >= 0)) return v;
  else                      return v == 0 ? 0 : v + y;
}

// Integer Division; regardless pos/neg
ll divFloor(ll x, ll y) {
  if (x > 0) {
    if (y > 0) return x / y;
    else       return (x - y - 1) / y;
  }else {
    if (y > 0) return (x - y + 1) / y;
    else       return x / y;
  }
}

ll divCeil(ll x, ll y) {
  if (x > 0) {
    if (y > 0) return (x + y - 1) / y;
    else       return x / y;
  }else {
    if (y > 0) return x / y;
    else       return (x + y + 1) / y;
  }
}

// ---- end intDiv
// ---- inserted library file mod.cc

/*
  You may want to put something like:
#define CONSTANT_MOD (1e9 + 7)
#define CONSTANT_MOD 998244353
  in the header part (outside of library paste area)
 */

struct Fp {
#if defined(CONSTANT_MOD)
  static const ll MOD = CONSTANT_MOD;
#else
  static ll MOD;
#endif

  ll val;

  /*
  ll _calc_from_ll(ll t = 0) {
    if      (t >= MOD)  return t % MOD;
    else if (t >= 0)    return t;
    else if (t >= -MOD) return t + MOD;
    else {
      ll v = t % MOD;
      if (v == 0) return 0;
      else        return v + MOD;
    }
  }
  */

  Fp(ll t = 0) : val(imod(t, MOD)) {}
  Fp(const Fp& t) : val(t.val) {}
  Fp& operator =(const Fp& t) { val = t.val; return *this; }
  Fp& operator =(ll t) { val = imod(t, MOD); return *this; }
  Fp& operator =(int t) { val = imod(t, MOD); return *this; }

  Fp& operator +=(const Fp& t) {
    val += t.val;
    if (val >= MOD) val -= MOD;
    return *this;
  }

  Fp& operator -=(const Fp& t) {
    val -= t.val;
    if (val < 0) val += MOD;
    return *this;
  }

  Fp& operator *=(const Fp& t) {
    val = (val * t.val) % MOD;
    return *this;
  }

  Fp inv() const {
    if (val == 0) {
      cerr << "inv() is called for zero." << endl;
      exit(1);
    }
    ll u = 0;
    ll v = 0;
    eGCD(val, MOD, u, v);
    return Fp(u);
  }

  Fp& operator /=(const Fp& t) {
    return (*this) *= t.inv();
  }

  Fp operator +(const Fp& t) const { return Fp(val) += t; }
  Fp operator -(const Fp& t) const { return Fp(val) -= t; }
  Fp operator *(const Fp& t) const { return Fp(val) *= t; }
  Fp operator /(const Fp& t) const { return Fp(val) /= t; }
  Fp operator -() const { return Fp(-val); }

  bool operator ==(const Fp& t) const { return val == t.val; }
  bool operator !=(const Fp& t) const { return val != t.val; }
  
  operator ll() const { return val; }

};

Fp operator +(int x, const Fp& y) { return Fp(x) + y; }
Fp operator -(int x, const Fp& y) { return Fp(x) - y; }
Fp operator *(int x, const Fp& y) { return Fp(x) * y; }
Fp operator /(int x, const Fp& y) { return Fp(x) / y; }
Fp operator +(ll x, const Fp& y) { return Fp(x) + y; }
Fp operator -(ll x, const Fp& y) { return Fp(x) - y; }
Fp operator *(ll x, const Fp& y) { return Fp(x) * y; }
Fp operator /(ll x, const Fp& y) { return Fp(x) / y; }
Fp operator +(const Fp& x, int y) { return x + Fp(y); }
Fp operator -(const Fp& x, int y) { return x - Fp(y); }
Fp operator *(const Fp& x, int y) { return x * Fp(y); }
Fp operator /(const Fp& x, int y) { return x / Fp(y); }
Fp operator +(const Fp& x, ll y) { return x + Fp(y); }
Fp operator -(const Fp& x, ll y) { return x - Fp(y); }
Fp operator *(const Fp& x, ll y) { return x * Fp(y); }
Fp operator /(const Fp& x, ll y) { return x / Fp(y); }

istream& operator>> (istream& is, Fp& t) {
  ll x; is >> x;
  t = x;
  return is;
}

ostream& operator<< (ostream& os, const Fp& t) {
  os << t.val;
  return os;
}

class Comb {
  int nMax;
  vector<Fp> vFact;
  vector<Fp> vInvFact;
public:
  Comb(int nm) : nMax(nm), vFact(nm+1), vInvFact(nm+1) {
    vFact.at(0) = 1;
    for (int i = 1; i <= nMax; i++) vFact.at(i) = i * vFact.at(i-1);
    vInvFact.at(nMax) = vFact.at(nMax).inv();
    for (int i = nMax; i >= 1; i--) vInvFact.at(i-1) = i * vInvFact.at(i);
  }
  Fp fact(int n) { return vFact.at(n); }
  Fp comb(int n, int r) {
    return vFact.at(n) * vInvFact.at(r) * vInvFact.at(n-r);
  }
  // The number of permutation extracting r from n.
  Fp perm(int n, int r) {
    return vFact.at(n) * vInvFact.at(n-r);
  }
};

#if !defined(CONSTANT_MOD)
ll Fp::MOD = 1e9 + 7;
// ll Fp::MOD = 998244353;
#endif

// ---- end mod.cc
// ---- inserted function power from util.cc
/* *** WARNING ***  
      ll x = power(10, 12) 
   does not work since it is interpreted as 
      ll x = power<int>((int)10, 12)
   Use power<ll>(10, 12) or power(10LL, 12).
 */
template<typename T>
T power(T a, ll b) {
  T twoPow = a;
  T rv(1);
  while (b > 0) {
    if (b & 1LL) rv *= twoPow;
    twoPow *= twoPow;
    b >>= 1;
  }
  return rv;
}

// ad-hoc power function
template<typename T, typename Op>
T ah_power(T a, ll b, const T& unit_t, Op op) {
  T two_pow = a;
  T ret = unit_t;
  while (b > 0) {
    if (b & 1LL) ret = op(ret, two_pow);
    two_pow = op(two_pow, two_pow);
    b >>= 1;
  }
  return ret;
}
// ---- end power
// @@ !! LIM  -- end mark --

int main(/* int argc, char *argv[] */) {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << setprecision(20);

  auto combi = [&](ll n, ll r) -> Fp {
    Fp p(1), q(1);
    for (ll i = 0; i < r; i++) {
      p *= n - i;
      q *= r - i;
    }
    return p / q;
  };

  ll n, a, b; cin >> n >> a >> b;
  cout << power<Fp>(2, n) - 1 - combi(n, a) - combi(n, b) << endl;

  return 0;
}



Measured memory_bytes: 3624