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

typedef long long ll;
ll mod = 1000000000 + 7;

ll modpow(ll a, ll n, ll mod){
  ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}

ll nCr(ll n, ll r, ll mod){
  ll res = n;
  for(int i = 2; i <= r; i++){
    res = res * (n + 1 - i) % mod;
    res = res * modpow(i, mod -2, mod) % mod;
  }
  return res;
}

int main(){
  ll n,a,b;
  cin >> n >> a >> b;

  ll ans = modpow(2, n, mod) - nCr(n, a, mod) - nCr(n,b,mod) - 1;
  ans = ans + mod + mod + mod;
  ans = ans % mod;
  cout << ans << endl;
}