#include <iostream>
using namespace std;
const int p = 1e9 + 7, N = 2e5 + 10;
int n, a, b;
typedef long long ll;

int qmi(int a, int b) {
    int res = 1;
    while (b) {
        if (b & 1)
            res = (ll)res * a % p;
        a = (ll)a * a % p;
        b >>= 1;
    }
    return res;
}

int C(int a, int b) {
    int res = 1;
    for (int i = 1, j = a; i <= b; i++, j--) {
        res = (ll)res * j % p;
        res = (ll)res * qmi(i, p - 2) % p;
    }
    return res;
}

int main() {
    cin >> n >> a >> b;
    int res = qmi(2, n);
    res = ((res - C(n, a)) % p + p) % p;
    res = ((res - C(n, b)) % p + p) % p;
    cout << res - 1;
}