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

const long mod = 1000000007; 

long pmod(long b, long e) {
  if (e == 0) return 1;
  if (e % 2 == 1) return b * pmod(b, e - 1) % mod;
  long t = pmod(b, e / 2);
  return t * t % mod;
}

long inv(long n) {
  return pmod(n, mod - 2);
}

long comb(long n, long r) {
  long prod = 1;
  for (int i = 0; i < r; ++i) {
    prod = prod * (n - i) % mod * inv(r - i) % mod;
  }
  return prod;
}

int n, a, b;
int main() {
  cin >> n >> a >> b;
  long sum = pmod(2, n);
  sum += mod - comb(n, a);
  sum += mod - comb(n, b);
  sum += mod - 1;
  cout << sum % mod << endl;
}