#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
#define rep(i,m,n) for(int i=m;i<n;i++)
ll mod=1e9+7;

ll power(ll x,ll n){
    if(n==0) return 1;
    ll res=power(x*x%mod,n/2);
    if(n&1) res=res*x%mod;
    return res;
}

int main(){
  ll n;
  int a,b;
  cin>>n>>a>>b;
  ll ans=power(2,n)-1;
  ll c=1;
  ll d=1;
  rep(i,0,a) {
    c=c*(n-i)%mod;
    d=d*(i+1)%mod;
  }
  ans-=c*power(d,1e9+5)%mod;
  c=1;
  d=1;
  rep(i,0,b) {
    c=c*(n-i)%mod;
    d=d*(i+1)%mod;
  }
  ans-=c*power(d,1e9+5)%mod;
  while(ans<0) ans+=mod;
  cout<<ans<<endl;
}