/*
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	@TT_beginner
	*/
#include <bits/stdc++.h>
using namespace std;
#define ok1 cerr<<"ok1\n";
#define ok2 cerr<<"ok2\n";
#define M LLONG_MAX
#define rep(i,n) for(int i=0;i<n;++i)
#define REP(i,s,n) for(int i=(s);i<(n);++i)
#define repr(i,n) for(int i=n-1;i>=0;--i)
#define REPR(i,s,n) for(int i=(s);i>=(n);--(i))
#define all(a) (a).begin(),(a).end()
#define reall(a) (a).rbegin(),(a).rend()
#define pb emplace_back //emplace_backの方が早いが慣れているため
#define DOUBLE fixed << setprecision(15)
#define fi first
#define se second
#define mp make_pair
#define mt make_tuple
const double pi = acos(-1.0L);
typedef vector<int> vi;
typedef vector<string> vs;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<char> vc;
typedef vector<double> vd;
typedef vector<bool> vb;
typedef deque<ll> dll;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> TLL;
typedef vector<P> vP;
typedef vector<TLL> vTLL;
const ll mod = 1e9 + 7;
//const ll mod = 998244353;
ll dy[4] = { 1,0,-1,0 };
ll dx[4] = { 0,1,0,-1 };
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class A, class B>
  ostream& operator<<(ostream& ost, const pair<A, B>&p) {
  ost << "{ " << p.first << ", " << p.second << " }";
  return ost;
}
template<class T>
  ostream& operator<<(ostream& ost, const vector<T>&v) {
  ost << "{ ";
  for (int i = 0; i<v.size(); i++) {
    if (i)ost << ", ";
    ost << v[i];
  }
  ost << " }";
  return ost;
}
template<class A, class B>
  ostream& operator<<(ostream& ost, const map<A, B>&v) {
  ost << "{ ";
  for (auto p : v) {
    ost << "{ " << p.first << ", " << p.second << " }";
  }
  ost << " }";
  return ost;
}
bool out_check(ll a, ll b) { return (0 <= a && a < b); }
double pitagoras(ll a, ll b, ll c, ll d) {
  double dx = a - b, dy = c - d;
  return pow(dx * dx + dy * dy, 0.5);
}
ll modpow(ll a, ll b) { ll c = 1; while (b > 0) { if (b & 1) { c = a * c%mod; }a = a * a%mod; b >>= 1; }return c; }
void Yes(bool x) { cout << ((x) ? "Yes\n" : "No\n"); }
void YES(bool x) { cout << ((x) ? "YES\n" : "NO\n"); }
void yes(bool x) { cout << ((x) ? "yes\n" : "no\n"); }
void Yay(bool x) { cout << ((x) ? "Yay!\n" : ":(\n"); }


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


int main() {
  cin.tie(0); ios::sync_with_stdio(false);//not intractive
  ll n, a, b;
  cin >> n >> a >> b;
  // Σ(0~r)nCr = 2^nより、Σ(1~r)nCr = 2^n - 1
  // 証明は二項定理より、(a+b)^n = Σ(i,0~n)nCr a^(n-i)*b^(i)　に(a,b)=(1,1)を代入で求まる
  cout << (modpow(2, n) - nCr(n, a) - nCr(n, b) - 1 + 2*mod) % mod << endl;
  //cerr<<nCr(n,a)<<" "<<nCr(n,b)<<endl;
}

Measured memory_bytes: 256