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

ll fast(ll a, ll n, ll m) {
    if (n == 0)
        return 1;
    else if (n % 2 == 1) {
        return fast(a, n - 1, m) * a % m;
    } else {
        ll tem = fast(a, n / 2, m) % m;
        return tem * tem % m;
    }
}
ll A(ll n, ll m, ll mod) {
    ll res = 1;
    for (int i = 1; i <= m; i++) {
        res = res * (n - i + 1) % mod;
    }
    for (int i = 1; i <= m; i++) {
        res = res * fast(i, mod - 2, mod) % mod;
    }

    return res;
}

int main() {
    ll n, a, b;
    cin >> n >> a >> b;
    ll mod = 1e9 + 7;
    ll res = fast(2, n, mod);
    res = (res - 1 - A(n, a, mod) - A(n, b, mod) + 2 * mod) % mod;
    cout << res;
}