text: // atcoder/abc156/D/main.cpp
  // author: @___Johniel
  // github: https://github.com/johniel/
  
  #include <bits/stdc++.h>
  
  #define each(i, c) for (auto& i : c)
  #define unless(cond) if (!(cond))
  
  using namespace std;
  
  template<typename P, typename Q> ostream& operator << (ostream& os, pair<P, Q> p) { os << "(" << p.first << "," << p.second << ")"; return os; }
  template<typename P, typename Q> istream& operator >> (istream& is, pair<P, Q>& p) { is >> p.first >> p.second; return is; }
  template<typename T> ostream& operator << (ostream& os, vector<T> v) { os << "("; for (auto& i: v) os << i << ","; os << ")"; return os; }
  template<typename T> istream& operator >> (istream& is, vector<T>& v) { for (auto& i: v) is >> i; return is; }
  template<typename T> ostream& operator << (ostream& os, set<T> s) { os << "#{"; for (auto& i: s) os << i << ","; os << "}"; return os; }
  template<typename K, typename V> ostream& operator << (ostream& os, map<K, V> m) { os << "{"; for (auto& i: m) os << i << ","; os << "}"; return os; }
  
  template<typename T> inline T setmax(T& a, T b) { return a = std::max(a, b); }
  template<typename T> inline T setmin(T& a, T b) { return a = std::min(a, b); }
  template<typename P, typename Q> inline pair<Q, P> reverse(pair<P, Q> p) { return make_pair(p.second, p.first); }
  
  using lli = long long int;
  using ull = unsigned long long;
  using point = complex<double>;
  using str = string;
  template<typename T> using vec = vector<T>;
  
  template<int MOD> struct Fp {
      long long val;
      constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
          if (val < 0) val += MOD;
      }
      constexpr int getmod() { return MOD; }
      constexpr Fp operator - () const noexcept {
          return val ? MOD - val : 0;
      }
      constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
      constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
      constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
      constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
      constexpr Fp& operator += (const Fp& r) noexcept {
          val += r.val;
          if (val >= MOD) val -= MOD;
          return *this;
      }
      constexpr Fp& operator -= (const Fp& r) noexcept {
          val -= r.val;
          if (val < 0) val += MOD;
          return *this;
      }
      constexpr Fp& operator *= (const Fp& r) noexcept {
          val = val * r.val % MOD;
          return *this;
      }
      constexpr Fp& operator /= (const Fp& r) noexcept {
          long long a = r.val, b = MOD, u = 1, v = 0;
          while (b) {
              long long t = a / b;
              a -= t * b; swap(a, b);
              u -= t * v; swap(u, v);
          }
          val = val * u % MOD;
          if (val < 0) val += MOD;
          return *this;
      }
      constexpr bool operator == (const Fp& r) const noexcept {
          return this->val == r.val;
      }
      constexpr bool operator != (const Fp& r) const noexcept {
          return this->val != r.val;
      }
      friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
          return os << x.val;
      }
      friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
          if (n == 0) return 1;
          auto t = modpow(a, n / 2);
          t = t * t;
          if (n & 1) t = t * a;
          return t;
      }
  };
  
  constexpr lli mod = 1e9 + 7;
  constexpr int N = 2 * 1e5 + 5;
  using mint = Fp<mod>;
  
  int main(int argc, char *argv[])
  {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
  
    lli n, a, b;
    while (cin >> n >> a >> b) {
      mint x = modpow(mint(2), n);
      x = x - mint(1);
  
      mint y(1);
      for (int i = 0; i < a; ++i) {
        y *= mint(n - i);
        y /= mint(i + 1);
      }
  
      mint z(1);
      for (int i = 0; i < b; ++i) {
        z *= mint(n - i);
        z /= mint(i + 1);
      }
  
      cout << x - y - z << endl;
    }
  
    return 0;
  }
  