/* #region Head */

#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

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

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pll = pair<ll, ll>;
template <class T>
using vc = vector<T>;
template <class T>
using vvc = vc<vc<T>>;
using vll = vc<ll>;
using vvll = vvc<ll>;
using vld = vc<ld>;
using vvld = vvc<ld>;
using vs = vc<string>;
using vvs = vvc<string>;
template <class T, class U>
using um = unordered_map<T, U>;

#define REP(i, m, n) for (ll i = (m), i##_len = (ll)(n); i < i##_len; ++(i))
#define REPM(i, m, n) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; ++(i))
#define REPR(i, m, n) for (ll i = (m), i##_min = (ll)(n); i >= i##_min; --(i))
#define REPD(i, m, n, d) for (ll i = (m), i##_len = (ll)(n); i < i##_len; i += (d))
#define REPMD(i, m, n, d) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; i += (d))
#define REPI(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define ALL(x) begin(x), end(x)
#define SIZE(x) ((ll)(x).size())
#define PREM(c)   \
    sort(all(c)); \
    for (bool c##p = 1; c##p; c##p = next_permutation(all(c)))
#define UNIQ(v) v.erase(unique(ALL(v)), v.end());

constexpr ll INF = 1'010'000'000'000'000'017LL;
constexpr ll MOD = 1'000'000'007LL; // 1e9 + 7
constexpr ld EPS = 1e-12;
constexpr ld PI = 3.14159265358979323846;

// vector 入力
template <typename T>
istream &operator>>(istream &is, vc<T> &vec)
{
    for (T &x : vec)
        is >> x;
    return is;
}

// vector 出力 (for dump)
template <typename T>
ostream &operator<<(ostream &os, vc<T> &vec)
{
    ll len = SIZE(vec);
    os << "{";
    for (int i = 0; i < len; i++)
        os << vec[i] << (i == len - 1 ? "" : ", ");
    os << "}";
    return os;
}

// vector 出力 (inline)
template <typename T>
ostream &operator>>(ostream &os, vc<T> &vec)
{
    ll len = SIZE(vec);
    for (int i = 0; i < len; i++)
        os << vec[i] << (i == len - 1 ? "\n" : " ");
    return os;
}

// pair 入力
template <typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &pair_var)
{
    is >> pair_var.first >> pair_var.second;
    return is;
}

// pair 出力
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var)
{
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}

// map 出力
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var)
{
    os << "{";
    REPI(itr, map_var)
    {
        os << *itr;
        itr++;
        if (itr != map_var.end())
            os << ", ";
        itr--;
    }
    os << "}";
    return os;
}

// um 出力
template <typename T, typename U>
ostream &operator<<(ostream &os, um<T, U> &map_var)
{
    os << "{";
    REPI(itr, map_var)
    {
        os << *itr;
        auto itrcp = itr;
        itrcp++;
        if (itrcp != map_var.end())
            os << ", ";
    }
    os << "}";
    return os;
}

// set 出力
template <typename T>
ostream &operator<<(ostream &os, set<T> &set_var)
{
    os << "{";
    REPI(itr, set_var)
    {
        os << *itr;
        itr++;
        if (itr != set_var.end())
            os << ", ";
        itr--;
    }
    os << "}";
    return os;
}

// dump
#define DUMPOUT cerr
void dump_func()
{
    DUMPOUT << endl;
}
template <class Head, class... Tail>
void dump_func(Head &&head, Tail &&... tail)
{
    DUMPOUT << head;
    if (sizeof...(Tail) > 0)
    {
        DUMPOUT << ", ";
    }
    dump_func(move(tail)...);
}

// chmax (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>>
bool chmax(T &xmax, const U &x, Comp comp = {})
{
    if (comp(xmax, x))
    {
        xmax = x;
        return true;
    }
    return false;
}

// chmin (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>>
bool chmin(T &xmin, const U &x, Comp comp = {})
{
    if (comp(x, xmin))
    {
        xmin = x;
        return true;
    }
    return false;
}

// ローカル用
#define DEBUG_

#ifdef DEBUG_
#define DEB
#define dump(...)                                                       \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                     \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" \
            << endl                                                     \
            << "    ",                                                  \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif

struct AtCoderInitialize
{
    static constexpr int IOS_PREC = 15;
    static constexpr bool AUTOFLUSH = false;

    AtCoderInitialize()
    {
        ios_base::sync_with_stdio(false);
        cin.tie(nullptr);
        cout.tie(nullptr);
        cout << fixed << setprecision(IOS_PREC);
        if (AUTOFLUSH)
            cout << unitbuf;
    }
} ATCODER_INITIALIZE;

/* #endregion */

struct mint
{
    ll x;
    mint(ll x = 0) : x((x % MOD + MOD) % MOD) {}
    mint &operator+=(const mint a)
    {
        if ((x += a.x) >= MOD)
            x -= MOD;
        return *this;
    }
    mint &operator-=(const mint a)
    {
        if ((x += MOD - a.x) >= MOD)
            x -= MOD;
        return *this;
    }
    mint &operator*=(const mint a)
    {
        (x *= a.x) %= MOD;
        return *this;
    }
    mint operator+(const mint a) const
    {
        mint res(*this);
        return res += a;
    }
    mint operator-(const mint a) const
    {
        mint res(*this);
        return res -= a;
    }
    mint operator*(const mint a) const
    {
        mint res(*this);
        return res *= a;
    }
    // O(log(t))
    mint pow(ll t) const
    {
        if (!t)
            return 1;
        mint a = pow(t >> 1); // ⌊t/2⌋ 乗
        a *= a;               // ⌊t/2⌋*2 乗
        if (t & 1)            // ⌊t/2⌋*2 == t-1 のとき
            a *= *this;       // ⌊t/2⌋*2+1 乗 => t 乗
        return a;
    }

    // for prime mod
    mint inv() const
    {
        return pow(MOD - 2); // オイラーの定理から， x^(-1) ≡ x^(p-2)
    }
    mint &operator/=(const mint a)
    {
        return (*this) *= a.inv();
    }
    mint operator/(const mint a) const
    {
        mint res(*this);
        return res /= a;
    }
    bool operator==(const mint a) const
    {
        return this->x == a.x;
    }
    bool operator==(const ll a) const
    {
        return this->x == a;
    }

    // mint 入力
    friend istream &operator>>(istream &is, mint &x)
    {
        is >> x.x;
        return is;
    }

    // mint 出力
    friend ostream &operator<<(ostream &os, mint x)
    {
        os << x.x;
        return os;
    }
};

class Combinaion
{
private:
    /* テーブルの大きさの既定値．(MAX)! まで計算できる． */
    static constexpr ll MAX = 1e6 + 11;
    /* 実際のテーブルの大きさ． */
    ll max;
    /* 階乗を格納するテーブル．fac[n] := n! % MOD. */
    vc<mint> fac;
    /* 階乗の逆元を格納するテーブル．finv[n] := (fac[n])^(-1). */
    vc<mint> finv;

    /* 各種テーブルを初期化する． */
    void init(int n)
    {
        max = n;
        fac[0] = fac[1] = 1;
        finv[0] = finv[1] = 1;
        REPM(i, 2, n)
        {
            fac[i] = fac[i - 1] * i;
        }
        finv[n] = fac[n].inv();
        REPR(i, n, 2)
        {
            finv[i - 1] = finv[i] * i;
        }
    }

public:
    /* コンストラクタ． */
    Combinaion(int n = MAX) : fac(n + 1), finv(n + 1)
    {
        init(n);
    }

    /* 二項係数 nCk % MOD を計算する． */
    mint operator()(ll n, ll k) const
    {
        assert(n <= max); // ここで詰まると RE
        assert(k <= max);
        if (n < k || n < 0 || k < 0)
            return 0;
        return fac[n] * finv[k] * finv[n - k];
    }
};

mint combination(ll n, ll k)
{
    // n! / (k! (n-k)!)
    mint ret = 1;
    REPM(i, 1, min(k, n - k))
    {
        ret *= n - i + 1;
        ret /= i;
    }
    return ret;
}

/**
Problem
 */
void solve()
{
    ll n, a, b;
    cin >> n >> a >> b;

    // Combinaion c;
    mint ret = mint(2).pow(n) - 1;
    ret -= combination(n, a);
    ret -= combination(n, b);
    cout << ret << endl;
}

/**
 * エントリポイント．
 * @return 0.
 */
int main()
{
    solve();
    return 0;
}


Measured memory_bytes: 256