#include <bits/stdc++.h>
#define rep(i, n, m) for (int i = (int)(n); i < (int)(m); i++)
#define repr(i, n, m) for (int i = (int)(n) - 1; i >= (int)(m); i--)
using namespace std;
using ll = int64_t;
const int MOD = 1000000007; // 10^9+7

// modint: mod 計算を int を扱うように扱える構造体
struct mod_int {
    ll val;
    constexpr mod_int(ll v = 0) noexcept : val(v % MOD) {
        if (val < 0) val += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr mod_int operator - () const noexcept {
        return val ? MOD - val : 0;
    }
    constexpr mod_int operator + (const mod_int& r) const noexcept { return mod_int(*this) += r; }
    constexpr mod_int operator - (const mod_int& r) const noexcept { return mod_int(*this) -= r; }
    constexpr mod_int operator * (const mod_int& r) const noexcept { return mod_int(*this) *= r; }
    constexpr mod_int operator / (const mod_int& r) const noexcept { return mod_int(*this) /= r; }
    constexpr mod_int& operator += (const mod_int& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr mod_int& operator -= (const mod_int& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr mod_int& operator *= (const mod_int& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr mod_int& operator /= (const mod_int& r) noexcept {
        ll a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            ll t = a / b;
            ll tmp = 0;
            a -= t * b; tmp = a; a = b; b = tmp;
            u -= t * v; tmp = u; u = v; v = tmp;
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator == (const mod_int& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator != (const mod_int& r) const noexcept {
        return this->val != r.val;
    }
    friend ostream& operator << (ostream &os, const mod_int& x) noexcept {
        return os << x.val;
    }
    friend constexpr mod_int modpow(const mod_int &a, ll n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};

using mint = mod_int;

// vector<ll> fac;
// vector<ll> finv, inv; // いらないときはコメントアウト

// // テーブルを作る前処理
// void com_init(int max){
//     fac.resize(max + 1);
//     finv.resize(max + 1);
//     inv.resize(max + 1);
//     fac[0] = fac[1] = 1;
//     finv[0] = finv[1] = 1;
//     inv[1] = 1;
//     for (int i = 2; i < max + 1; i++){
//         fac[i] = fac[i - 1] * i % MOD;
//         inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
//         finv[i] = finv[i - 1] * inv[i] % MOD;
//     }
// }

// // 二項係数計算
// ll com(int n, int k){
//     if (n < k) return 0;
//     if (n < 0 || k < 0) return 0;
//     return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
// }

vector<mint> com;
void com_init(int n, int maxK) {
    com.resize(maxK + 1);
    com[0] = 0;
    com[1] = n;
    rep(i, 2, maxK + 1)
    {
        com[i] = com[i - 1] * (n - i + 1) / i;
    }
}

int main() {
// https://atcoder.jp/contests/abc156/tasks/abc156_d
    int n, a, b;
    cin >> n >> a >> b;
    mint total = modpow(mint(2), n) - 1;
    com_init(n, 200000);
    cout << total - com[a] - com[b] << endl;
}


Measured memory_bytes: 1792