#include <bits/stdc++.h>
using namespace std;

#define SORT(c) sort((c).begin(), (c).end())
#define REVERSE(v) reverse((v).begin(), (v).end())
#define ANS(ans) cout << (ans) << endl;
#define UNIQUE(v) (v).erase(unique((v).begin(), (v).end()), (v).end());
typedef vector<int> VI;
typedef pair<int, int> P;

//repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i <= (b); ++i)
#define REP(i, n) for (int i = 0; i < (n); ++i)

// modint: mod 計算を int を扱うように扱える構造体
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;
    }
};


const int MOD = 1000000007;
using mint = Fp<MOD>;

// a^n mod を計算する
long long modpow(long long a, long long n)
{
  long long res = 1;
  while (n > 0)
  {
    if (n & 1)
      res = res * a % MOD;
    a = a * a % MOD;
    n >>= 1;
  }
  return res;
}

mint modpow2(int a, long long n)
{
  mint res = 1;
  REP(i,n){
    res *= a;
  }
  return res;
}

long long com(long long n, long long k)
{
  long long ret = 1;
  FOR(i, 1, k)
  {
    long long check =  (ret%MOD) * (n - i + 1);
    if(check<0){
      cout << "error" << endl;
    }
    ret = (ret%MOD) * (n - i + 1) / i % MOD;
  }
  return ret%MOD;
}

mint com2(long long n, long long k)
{
  mint ret = 1;
  FOR(i, 1, k)
  {
    ret = ret * (n - i + 1) / i ;
  }
  return ret;
}

int main()
{
  int n, a, b;
  cin >> n >> a >> b;

  // long long na = com(n, a);
  // long long nb = com(n, b);

  // long long mi = na + nb + 1;

  // long long s = modpow(2, n);

  mint na = com2(n,a);
  mint nb = com2(n,b);
  mint s = modpow(2,n);
  ANS(s - na - nb - 1);

  // while (true)
  // {
  //   if (s - mi< 0)
  //   {
  //     s += MOD;
  //   }
  //   else
  //   {
  //     ANS(s - mi);
  //     break;
  //   }
  // }

  return 0;
}


Measured memory_bytes: 256