#include<bits/stdc++.h>

#ifdef _PRINTDEBUG
  #include "lib/printdebug.hpp"
#else
  #define printdebug(...) 1
#endif
#define I1000000007 (1000000007)
#define I998244353   (998244353)
#define IINF             (1<<28)
#define LINF           (1LL<<60)
#define ALL(a)         (a).begin(), (a).end()
#define rep(i, n)      REP(i, 0, (n))
#define repc(i, n)     REPC(i, 0, (n))
#define REP(i, n, m)   for (int i = (int)(n); i <  (int)(m); i++)
#define REPC(i, n, m)  for (int i = (int)(n); i <= (int)(m); i++)
#define REPCM(i, n, m) for (int i = (int)(n); i >= (int)(m); i--)
#define yesno(cond)       YESNO((cond), "Yes", "No")
#define YESNO(cond, a, b) cout << ((cond) ? (a) : (b)) << "\n"
template<class T> inline bool chmin(T& a, const T& b) {
  if (a > b) { a = b; return true; } else return false;
}
template<class T> inline bool chmax(T& a, const T& b) {
  if (a < b) { a = b; return true; } else return false;
}
template<std::int_fast64_t divisor> struct modint {
  using i64 = std::int_fast64_t;

  i64 val;

  constexpr modint(i64 v = 0) noexcept : val(v % divisor) {
    if (val < 0) val += divisor;
  }

  constexpr modint operator + (const modint& rhs) const noexcept {
    return modint(*this) += rhs;
  }

  constexpr modint operator - (const modint& rhs) const noexcept {
    return modint(*this) -= rhs;
  }

  constexpr modint operator * (const modint& rhs) const noexcept {
    return modint(*this) *= rhs;
  }

  constexpr modint operator / (const modint& rhs) const noexcept {
    return modint(*this) /= rhs;
  }

  constexpr modint operator ~ () const noexcept {
    i64 a = this->val, b = divisor, u = 1, v = 0;
    while (b > 0) {
      i64 t = a / b;
      a -= t * b;
      u -= t * v;
      i64 c = a; a = b; b = c;
      i64 w = u; u = v; v = w;
    }
    if (u < 0) u += divisor;
    u %= divisor;
    return u;
  }

  constexpr modint& operator += (const modint& rhs) noexcept {
    val += rhs.val;
    if (val >= divisor) val -= divisor;
    return *this;
  }

  constexpr modint& operator -= (const modint& rhs) noexcept {
    if (val < rhs.val) val += divisor;
    val -= rhs.val;
    return *this;
  }

  constexpr modint& operator *= (const modint& rhs) noexcept {
    val = val * rhs.val % divisor;
    return *this;
  }

  constexpr modint& operator /= (const modint& rhs) noexcept {
    val = val * (~(modint(rhs))).val % divisor;
    return *this;
  }

  friend modint<divisor> modpow (modint<divisor> a, i64 n) noexcept {
    auto res = modint<divisor>(1);
    while(n > 0) {
      if(n&1) res *= a;
      a *= a;
      n >>= 1;
    }
    return res;
  }

  friend std::ostream& operator << (std::ostream& os, const modint<divisor>& a) noexcept {
    return os << a.val;
  }
};

namespace solver {
  using namespace std;
  using ll = long long;
  using mint = modint<I1000000007>;

  int N, A, B;

  void init() {
    cin >> N >> A >> B;
  }

  void solve() {
    mint ans = modpow(mint(2), N);
    mint a = 1;
    REPC(i, 1, B) {
      a = a * (N-i+1) / i;
      if(i == A || i == B) ans -= a;
    }
    ans -= 1;
    cout << ans << endl;
  }
}

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  solver::init();
  solver::solve();
  return 0;
}

Measured memory_bytes: 256