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

const int P = ll(1e9) + 7;
int pw(int x, int y) {
	int r = 1;
	for (; y; y >>= 1, x = 1ll * x * x % P)
		if (y & 1) r = 1ll * r * x % P;
	return r;
}

int n, a, b, ans, x, y;
int main() {
	cin >> n >> a >> b;
	ans = (pw(2, n) + P - 1) % P;
	x = y = 1;
	for (int i = 0; i < a; i++) {
		x = 1ll * x * (n - i) % P;
		y = y * (i + 1ll) % P;
	}
	ans = (ans + P - 1ll * x * pw(y, P - 2) % P) % P;

	x = y = 1;
	for (int i = 0; i < b; i++) {
		x = 1ll * x * (n - i) % P;
		y = y * (i + 1ll) % P;
	}
	ans = (ans + P - 1ll * x * pw(y, P - 2) % P) % P;

	cout << ans;
}