#include <bits/stdc++.h>
#define REP(i, n) for(int i = 0, i##_len = (n); i < i##_len; ++i)
#define REPS(i, _s, n) for(int i = _s, i##_len = (n); i < i##_len; ++i)
#define ALL(x) (x).begin(), (x).end()
using namespace std;

#define repi(itr, ds) for(auto itr = ds.begin(); itr != ds.end(); itr++)
// vector
template <typename T>
istream &operator>>(istream &is, vector<T> &vec) {
  for(T &x : vec) is >> x;
  return is;
}
// pair
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
  os << "(" << pair_var.first << ", " << pair_var.second << ")";
  return os;
}
// vector
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &vec) {
  os << "{";
  for(int i = 0; i < vec.size(); i++) {
    os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
  }
  os << "}\n   ";
  return os;
}
// map
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;
}
// set
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;
}

#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(std::move(tail)...);
}
#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

typedef long long int ll;

long myPow(long x, long n, long m) {
  if(n == 0) return 1;
  if(n % 2 == 0)
    return myPow(x * x % m, n / 2, m);
  else
    return x * myPow(x, n - 1, m) % m;
}

const int MAX = 510000;
ll MOD = 1000000007;
long long fac[MAX], finv[MAX], inv[MAX];

void combination_init() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for(int i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}

long long combination(int n, int k) {
  if(n < k) return 0;
  if(n < 0 || k < 0) return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
int main() {
  int n, a, b;
  cin >> n >> a >> b;

  ll sum = myPow(2, n, MOD) - 1;
  dump(sum);

  combination_init();
  ll x = n;
  ll a_diff = 1;
  REPS(i, 1, a + 1) {
    a_diff = a_diff * x % MOD;
    a_diff = a_diff * inv[i] % MOD;
    x--;
  }
  x = n;
  ll b_diff = 1;
  REPS(i, 1, b + 1) {
    b_diff = b_diff * x % MOD;
    b_diff = b_diff * inv[i] % MOD;
    x--;
  }
  dump(sum, a_diff, b_diff);
  ll ans = ((sum - a_diff) % MOD - b_diff) % MOD;
  if(ans < 0) {
    ans += MOD;
  }
  cout << ans << endl;
}


Measured memory_bytes: 12160