// D - Bouquet
#include <bits/stdc++.h>
using namespace std;
using ll = long long;

// a^n mod m を計算する(二分累乗法:O(logn))
ll modpow(ll a, ll n, ll m) {
	ll x = 1;
	while(n > 0){
		if(n & 1) x = x * a % m;
		a = a * a % m;
		n >>= 1;
	}
	return x;
}

// nCr mod m
ll nCr(ll n, ll r, ll m){
	ll a = 1, b = 1;
	for(ll i=1; i<=r; ++i){
		a *= n - i + 1;
		b *= i;
		a %=m;
		b %=m;
	}
	return a * modpow(b, m-2, m) % m;
}

int main(){
	ll MOD = 1000000007, N,A,B;
	cin>>N>>A>>B;
	ll ans = modpow(2, N, MOD) - 1;
	ans -= nCr(N, A, MOD);
	ans -= nCr(N, B, MOD);
	ans %= MOD;
	if(ans < 0L) ans += MOD;
	cout<< ans <<endl;
}