#include <bits/stdc++.h>
#define LL long long
using namespace std;
const int P = 1e9 + 7;
inline int qpow(int x,int y){
	static int r; r=1; while (y){ if (y&1) r=(LL)r*x%P;y>>=1,x=(LL)x*x%P; } return r;
}
inline int Inv(int x){
	return qpow(x,P-2);
}
inline int C(int n,int m){
	if (m>n) return 0;
	int ans = 1;
	for (int i = 1; i <= m; ++i) ans = (LL)ans *Inv(i) % P * (n-i+1) % P;
	return ans;
}
int n,a,b,ans;
int main(){
	cin >> n >> a >> b;
	ans = qpow(2,n) - C(n,a) - C(n,b) - 1;
	ans %= P; ans += P; ans %= P;
	cout << ans << endl;
    return 0;
}