#pragma region Macros
#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
using WGraph = vector<vector<pair<int, ll>>>;

template<class T>inline bool chmax(T &a, const T &b) { if (b > a) { a = b; return true; } return false; }
template<class T>inline bool chmin(T &a, const T &b) { if (b < a) { a = b; return true; } return false; }

constexpr int dx[4] = {-1, 0, 0, 1}, dy[4] = {0, -1, 1, 0};
constexpr int INF = 1e9;
constexpr int MOD = 1e9 + 7;
constexpr long long LINF = 1e18;
constexpr double EPS = 1e-10;
constexpr double PI = M_PI;
#pragma endregion

template<int mod = MOD>
class ModInt {
    private:
        long long val;
    public:
        ModInt(const long long v = 0) : val(v%mod) { if (val < 0) val += mod; }
        ModInt(const ModInt &v) : val(v.val) {}
        ModInt &operator=(const long long v) { val = v; return *this; }
        ModInt &operator=(const ModInt &v) { if (this != &v) val = v.val; return *this; }
        ModInt operator+() const { return ModInt(val); }
        ModInt operator-() const { return ModInt(-val); }
        ModInt operator+(const ModInt &v) const { return ModInt(*this) += v; }
        ModInt operator-(const ModInt &v) const { return ModInt(*this) -= v; }
        ModInt operator*(const ModInt &v) const { return ModInt(*this) *= v; }
        ModInt operator/(const ModInt &v) const { return ModInt(*this) /= v; }
        ModInt &operator+=(const ModInt &v) { val += v.val; if (val >= mod) val -= mod; return *this; }
        ModInt &operator-=(const ModInt &v) { val -= v.val; if (val < 0) val += mod; return *this; }
        ModInt &operator*=(const ModInt &v) { val *= v.val; if (val >= mod) val %= mod; return *this; }
        ModInt &operator/=(const ModInt &v) { val *= v.inverse(); if (val >= mod) val %= mod; return *this; }
        ModInt &operator++() { ++val; if (val >= mod) val -= mod; return *this; }
        ModInt &operator--() { --val; if (val < 0) val += mod; return *this; }
        ModInt operator++(int) { ModInt tmp(*this); operator++(); return tmp; }
        ModInt operator--(int) { ModInt tmp(*this); operator--(); return tmp; }
        bool operator==(const ModInt &v) const { return val == v.val; }
        bool operator!=(const ModInt &v) const { return !(*this == v); }
        friend istream &operator>>(istream &s, ModInt &v) { long long tmp; s >> tmp; v = ModInt(tmp); return s; }
        friend ostream &operator<<(ostream &s, const ModInt &v) { return s << v.val; }
        ModInt inverse() const {
            long long n = val, res = 1;
            while (n > 1) {
                res *= (mod - mod / n);
                res %= mod;
                n = mod % n;
            }
            return ModInt(res);
        }
        friend ModInt<MOD> modpow(ModInt v, long long n) {
            ModInt<MOD> res(1);
            for ( ; n>0; n>>=1) {
                if (n & 1) res *= v;
                v *= v;
            }
            return res;
        }
};

long long inv(long long n) {
    long long res = 1;
    while (n > 1) {
        res *= (MOD - MOD/n);
        res %= MOD;
        n = MOD % n;
    }
    return res;
}

long long comb_mod(long long n, long long r) {
    long long nume = 1;
    long long deno = 1;
    long long r_new = (r <= n/2) ? r : n-r;
    if (r_new < 0) {
        return 0;
    } else if (r_new == 0) {
        return 1;
    }

    for (long long i=1; i<=r_new; i++) {
        deno *= i % MOD;
        deno %= MOD;
    }
    for (long long i=n-r_new+1; i<=n; i++) {
        nume *= i % MOD;
        nume %= MOD;
    }
    deno = inv(deno);
    return (deno * nume) % MOD;
}

void solve() {
    int n, a, b;
    cin >> n >> a >> b;

    cout << ModInt<MOD>(modpow(ModInt<MOD>(2), n) - comb_mod(n, a) - comb_mod(n, b) - comb_mod(n, 0)) << '\n';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(20);

    solve();

    return 0;
}


Measured memory_bytes: 256