// Hack it and have it ;) //
/*author* Priyanshu Shrivastav (from IIT Palakkad) *
 * *_ __ ___  _ ______ ___  _ ____   ___  ___| |_  *
 * | '_ ` _ \| '__/ __/ _ \| '_ \ \ / / |/ __| __| *
 * | | | | | | | | (_| (_) | | | \ V /| | (__| |_  *
 * |_| |_| |_|_|(_)___\___/|_| |_|\_/ |_|\___|\__| *
When I wrote this, only God and I understood what I was doing
 ** * * * * * * * Now, only God knows!* * * * * * */
#include      <bits/stdc++.h> /*{{{*/
#include      <ext/pb_ds/assoc_container.hpp>
#include      <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

#ifndef CONVICTION
#pragma GCC       optimize ("Ofast")
#pragma GCC       optimize ("unroll-loops")
#pragma GCC       target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#endif

#define IOS       ios_base::sync_with_stdio(false); cin.tie (nullptr)
#define PREC      cout.precision (10); cout << fixed
#define X         first
#define Y         second
#define sz(x)     (int)x.size()
#define fr(i,x,y) for (int i = (int)x; i <= (int)y; ++i)
#define rv(i,x,y) for (int i = (int)x; i >= (int)y; --i)
#define cnt(x)    __builtin_popcount(x)
#define cntll(x)  __builtin_popcountll(x)
#define bg(x)     " [ " << #x << " : " << (x) << " ] "
#define un(x)     sort(x.begin(), x.end()), \
  x.erase(unique(x.begin(), x.end()), x.end())
using   ll  =     long long;
using   ull =     unsigned long long;
using   ff  =     long double;
using   pii =     pair<int,int>;
using   pil =     pair<int,ll>;
using   pll =     pair<ll,ll>;
using   vi  =     vector <int>;
using   vl  =     vector<ll>;
using   vvi =     vector <vi>;
using   vvl =     vector <vl>;
using   vp  =     vector <pii>;
using   vvp =     vector <vp>;
typedef tree
< int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
ordered_set;

struct chash {
  int operator () (pii x) const { return x.X*31 + x.Y; }
};
gp_hash_table <pii, int, chash> gmp;

#if __cplusplus > 201103L
seed_seq seq{
  (uint64_t) chrono::duration_cast<chrono::nanoseconds>
    (chrono::high_resolution_clock::now().time_since_epoch()).count(),
    (uint64_t) __builtin_ia32_rdtsc(),
    (uint64_t) (uintptr_t) make_unique<char>().get()
};
mt19937 rng(seq); //uniform_int_distribution<int> (l, h)(rng); //[low, high]
#else
auto seed = chrono::high_resolution_clock::now().time_since_epoch().count();
mt19937 rng(seed);
#endif

#define debug(args...) { \
  /* WARNING : do NOT compile this debug func calls with following flags: // \
   * // -D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC -D_FORTIFY_SOURCE=2*/ \
  string _s = #args; replace(_s.begin(), _s.end(), ',', ' ');\
  stringstream _ss(_s); \
  istream_iterator<string> _it(_ss); err(_it, args); \
}
void err(istream_iterator<string> it) {
  it->empty(); cerr << " (Line : " << __LINE__ << ")" << '\n';
}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
  cerr << fixed << setprecision(15)
    << " [ " <<  *it << " : " << a  << " ] "<< ' ';
  err(++it, args...);
}
//         __                                           __
//        (**)                                         (**)
//        IIII                                         IIII
//        ####                                         ####
//        HHHH     Madness comes, and madness goes     HHHH
//        HHHH    An insane place, with insane moves   HHHH
//        ####   Battles without, for battles within   ####
//     ___IIII___        Where evil lives,          ___IIII___
//  .-`_._"**"_._`-.      and evil rules         .-`_._"**"_._`-.
// |/``  .`\/`.  ``\|    Breaking them up,      |/``  .`\/`.  ``\|
// `     }    {     '  just breaking them in    `     }    {     '
//       ) () (  Quickest way out, quickest way wins  ) () (
//       ( :: )      Never disclose, never betray     ( :: )
//       | :: |   Cease to speak or cease to breath   | :: |
//       | )( |        And when you kill a man,       | )( |
//       | || |          you're a murderer            | || |
//       | || |             Kill many                 | || |
//       | || |        and you're a conqueror         | || |
//       | || |        Kill them all ... Ooh..        | || |
//       | || |           Oh you're a God!            | || |
//       ( () )                       -Megadeth       ( () )
//        \  /                                         \  /
//         \/                                           \/
/*}}}*/
/*****************************************************************************/
//Don’t practice until you get it right. Practice until you can’t get it wrong

const int Mod = (int)1e9 + 7;
inline int add (int x, int y) { return (x + y) % Mod; }
inline int sub (int x, int y) { return (x - y + Mod) % Mod; }
inline int mul (int x, int y) { return (int) (1ll*x*y % Mod); }
inline int pow (int x, int y) {
  int res = 1;
  while (y) {
    if (y & 1) res = mul(res, x);
    x = mul(x, x), y >>= 1;
  }
  return res;
}
inline int inv (int x) { return pow(x, Mod - 2); }
inline int dv (int x, int y) { return mul(x, inv(y)); }

const int MAXFAC = (int)1e6 + 10;
int fac[MAXFAC];
void init_fac () {
  fac[0] = 1;
  for (int i = 1; i < MAXFAC; ++i) fac[i] = mul(fac[i - 1], i);
}
inline int choose (int n, int r) {
  int num = fac[n];
  int den = mul(fac[n - r], fac[r]);
  return dv(num, den);
}

inline int cal (int n, int a) {
  int res = 1;
  for (int i = n-a+1; i <= n; ++i) {
    res = mul(res, i);
  }
  return dv(res, fac[a]);
}

signed main() {
  IOS; PREC;
  init_fac();

  int n, a, b;
  cin >> n >> a >> b;

  cout << sub(pow(2, n), add(cal(n, a), cal(n, b)))  - 1<< '\n';


  return EXIT_SUCCESS;
}



Measured memory_bytes: 4224