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

int base = 1e9 + 7;

ll invmod(ll p, ll q) {
  ll r = 1;
  while (q) {
    if (q&1) r = (r*p) % base;
    p = p*p % base;
    q >>= 1;
  }
  return r;
}

ll combimod(ll n, ll m) {
  ll t = 1;
  while (m) {
    t = t * n % base;
    t = t * invmod(m, base-2) % base;
    n--; m--;
  }
  return t;
}

int main() {
  ll n, a, b; cin >> n >> a >> b;
  
  ll total = invmod(2, n) - 1;
  total = (total + base - combimod(n, a)) % base;
  total = (total + base - combimod(n, b)) % base;
  
  cout << total << endl;
}