#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <ctime>
#include <iomanip>
#include <numeric>
#include <cmath>
using namespace std;
#define ll long long
#define endl '\n'
const int MAX = 2e5 + 4;
const int MOD = 1e9 + 7;
// Extended Euclidean algorithm
int xGCD(int a, int b, int& x, int& y) {
	if (b == 0) {
		x = 1;
		y = 0;
		return a;
	}

	int x1, y1, gcd = xGCD(b, a % b, x1, y1);
	x = y1;
	y = x1 - (long long)(a / b) * y1;
	return gcd;
}
ll fast_power(ll base, ll power)
{
	ll result = 1;
	while (power)
	{
		if (power & 1)
			result = (result * base) % MOD;
		base = (base * base) % MOD;
		power /= 2;
	}
	return result;
}
ll binomialCoeff(int n, int k)
{
	ll res = 1;
	if (k > n - k) k = n - k;
	for (int i = 0; i < k; i++)
	{
		res = res * (n - i) % MOD;
		res = res / (i + 1) % MOD;
	}
	return res;
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	int n, a, b;
	cin >> n >> a >> b;
	int result = fast_power(2, n) - 1;
	result -= binomialCoeff(n, a);
	result -= binomialCoeff(n, b);

	cout << result;
	return 0;
}