#include <bits/stdc++.h>
#define N 100005
#define ll long long
using namespace std;
ifstream in("in.txt");
const ll M=1000000007;
ll fortza(ll x, ll i){
    if(i==1){
        return x;
    }
    ll t=fortza(x,i/2);
    t=(t*t)%M;
    if(i&1){
        t=(t*x)%M;
    }
    return t;
}
int main(){
    ll n, a, b, x=1, t;
    cin>>n>>a>>b;
    for(ll i=1; i<=a; ++i){
        x=x*((n-i+1)*fortza(i, M-2)%M)%M;
    }
    t=(fortza(2, n)-1-x+M)%M;
    for(ll i=a+1; i<=b; ++i){
        x=x*((n-i+1)*fortza(i, M-2)%M)%M;
    }
    cout<<(t-x+M)%M;
    return 0;
}