/*
 * short          2^15-1 ~ 3e4
 * int, long x86  2^31-1 ~ 2e9
 * long long      2^63-1 ~ 9e18
 */
#include <bits/stdc++.h>
#define x first
#define y second
#define pb push_back
#define mp make_pair
#define fr(a, b) for (int a = 0; a < b; ++a)
using namespace std; typedef long long ll; const int inf = numeric_limits<int>::max(); void print() {cerr << endl;}
template<typename T, typename... Ts> void print(T&&a, Ts&&...etc) {cerr << a << ' '; print(etc...);}
template<typename T, typename U> ostream& operator<<(ostream& s, const pair<T,U>&p) {s << "<" << p.x << ", " << p.y << ">"; return s;} // ver. 2020-02-17
template<typename T> ostream& operator<<(ostream& s, const vector<T>&v) {s << "["; for (auto &x : v) s << x << ", "; if (!v.empty()) s << "\b\b"; s << "]"; return s;}
struct io{io(){ios_base::Init i; ios_base::sync_with_stdio(0); cin.tie(0);}}io;
const ll m = 1000000007;

ll fact[100] = {1, 682498929, 491101308, 76479948, 723816384, 67347853, 27368307, 625544428, 199888908, 888050723, 927880474, 281863274, 661224977, 623534362, 970055531, 261384175, 195888993, 66404266, 547665832, 109838563, 933245637, 724691727, 368925948, 268838846, 136026497, 112390913, 135498044, 217544623, 419363534, 500780548, 668123525, 128487469, 30977140, 522049725, 309058615, 386027524, 189239124, 148528617, 940567523, 917084264, 429277690, 996164327, 358655417, 568392357, 780072518, 462639908, 275105629, 909210595, 99199382, 703397904, 733333339, 97830135, 608823837, 256141983, 141827977, 696628828, 637939935, 811575797, 848924691, 131772368, 724464507, 272814771, 326159309, 456152084, 903466878, 92255682, 769795511, 373745190, 606241871, 825871994, 957939114, 435887178, 852304035, 663307737, 375297772, 217598709, 624148346, 671734977, 624500515, 748510389, 203191898, 423951674, 629786193, 672850561, 814362881, 823845496, 116667533, 256473217, 627655552, 245795606, 586445753, 172114298, 193781724, 778983779, 83868974, 315103615, 965785236, 492741665, 377329025, 847549272};

ll pw(ll a, ll n) {
    if (n == 0) return 1;
    if (n % 2) {
        return (a * pw(a, n-1)) % m;
    }
    ll a2 = pw(a, n/2);
    return (a2 * a2) % m;
}

ll f(ll n) {
    if (n < 2) return 1;
    ll ans = 1;
    ll j = 1;
    for (ll i = 1; i < 100; ++i) {
        if (n >= i * 10000000) {
            ans = fact[i];
            j = i * 10000000;
        }
    }
    // print("for n", n, " starting from", j, " ans", ans);
    for (++j; j <= n; ++j) {
        ans = (ans * j) % m;
    }
    return ans;
}

ll ch(ll n, ll k) {
    ll ans = f(n);
    ll x= f(k);
    ll y = f(n-k);
    ll t = pw((x * y) % m, m-2);
    return (ans * t) % m;
}

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

    ll t1, t2, t3;
    t1 = pw(2, n);
    // print("2*n", t1);

    ll tmp;
    ll f_n = f(n);
    // print("f(n)", f_n);

    ll f_a = f(a);
    // print("f(a)", f_a);
    ll f_n_a = f(n-a);
    // print("f(n-a)", f_n_a);
    tmp = pw((f_n_a * f_a) % m, m-2);
    t2 = (f_n * tmp) % m;
    // print("C_n^a", t2);

    ll f_b = f(b);
    // print("f(b)", f_b);
    ll f_n_b = f(n-b);
    // print("f(n-b)", f_n_b);
    tmp = pw((f_n_b * f_b) % m, m-2);
    t3 = (f_n * tmp) % m;
    // print("C_n^b", t3);

    ll ans = t1 - t2 - t3 - 1;
    ans %= m;
    ans = (ans + m) % m;
    cout << ans << endl;
    return 0;
}


Measured memory_bytes: 256