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

//#define int long long
//struct Fast {Fast(){std::cin.tie(0);ios::sync_with_stdio(false);}} fast;

/* short */
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define X real()
#define Y imag()

/* REPmacro */
#define REPS(i, a, n) for (LL i = (a); i < (LL)(n); ++i)
#define REP(i, n) REPS(i, 0, n)
#define DEPS(i, a, n) for (LL i = (a); i >= (LL)(n); --i)
#define DEP(i, n) DEPS(i, n, 0)
#define EACH(i, n) for (auto&& i = (n).begin(); i != (n).end(); ++i)
#define REACH(i, n) for (auto&& i = (n).rbegin(); i != (n).rend(); ++i)
#define FILL(arr,val) fill((arr), (arr)+sizeof(arr)/sizeof((arr)[0]), (val))

/* debug */
#define debug(x) cerr << x << " " << "(L:" << __LINE__ << ")" << '\n';

/* alias */
using LL = long long;
using ULL = unsigned long long;
using DBL = double;
using CPX = complex<DBL>;
using VI = vector<int>;
using VVI = vector<VI>;
using VVVI = vector<VVI>;
using VS = vector<string>;
using PII = pair<int, int>;
using PIS = pair<int, string>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const int INF = 1001001001;
const LL LINF = 1001001001001001001LL;
const int MOD = 1e9 + 7;
const DBL EPS = 1e-12;
const DBL PI=3.1415926535897932384626;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1};
const int dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool inside(int y, int x, int H, int W)
  {return y >= 0 && x >= 0 && y < H && x < W;}
inline int in()
  {int x; cin >> x; return x;}
inline LL IN()
  {LL x; cin >> x; return x;}
inline VS split(const string& t, char c)
  {VS v; stringstream s(t); string b; while(getline(s, b, c)) v.eb(b); return v;}
template <typename T> inline bool chmin(T& a, const T& b)
  {if (a > b) a = b; return a > b;}
template <typename T> inline bool chmax(T& a, const T& b)
  {if (a < b) a = b; return a < b;}
template <typename T, typename S> inline void print(const pair<T, S>& p)
  {cout << p.first << " " << p.second << endl;}
template <typename T> inline void print(const T& x)
  {cout << x << '\n';}
template <typename T, typename S> inline void print(const vector<pair<T, S>>& v)
  {for (auto&& p : v) print(p);}
template <typename T> inline void print(const vector<T>& v, string s = " ")
  {REP(i, v.size()) cout << v[i] << (i != (LL)v.size() - 1 ? s : "\n");}

/* modint */
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;
    }
};
using mint = Fp<MOD>;

/* nCr */
LL inv(LL x, LL mod) {
    LL res = 1;
    LL k = mod - 2;
    LL y = x;
    while (k) {
        if (k & 1) res = (res * y) % mod;
        y = (y * y) % mod;
        k /= 2;
    }
    return res;
}

LL C(int n, int r, int mod) {
  LL ret = 1;
  while(true){
    if(r == 0)break;
    int N = n % mod;
    int R = r % mod;
    if(N < R)return 0;

    for(int i = 0; i < R; i++) {
      ret = ret * (N-i) % mod;
    }
    long imul = 1;
    for(int i = 0; i < R; i++) {
      imul = imul * (i+1) % mod;
    }
    ret = ret * inv(imul, mod) % mod;
    n /= mod; r /= mod;
  }
  return ret;
}

signed main() {
  int N, A, B;
  cin >> N >> A >> B;
  mint two = 2;

  mint all = modpow(two, N) - 1;
  mint a = C(N,A,MOD);
  mint b = C(N,B,MOD);
  mint count = all - a - b;
  print(count);
  return 0;
}

Measured memory_bytes: 256