#include<bits/stdc++.h>
using namespace std;
#define int long long
int pow_mod(int n,int k,int m){
	int r=1;
	for(;k>0;k>>=1){
    	if(k&1) r=(r*n)%m;
		n=(n*n)%m;
 	}
	return r;
}
int fact_mod(int n,int i,int m){
  int k = n;
  int ans=1;
  while(k > n-i){
    ans = ans*k%m;
    k--;
  }
  return ans;
}
signed main(){
  int n,a,b,m = 1000000007;
  cin >> n >> a >>b;
  int sum = pow_mod(2,n,m)-1;
  sum -= fact_mod(n,a,m)*pow_mod(fact_mod(a,a,m),m-2,m)%m;
  sum -= fact_mod(n,b,m)*pow_mod(fact_mod(b,b,m),m-2,m)%m;
  while(sum<0)
    sum+=m;
  cout << sum<< endl;
}