#include <bits/stdc++.h>

#define mod 1000000007

typedef long long ll;

using namespace std;

ll qp(ll a, ll b) {
    ll res = 1;
    while (b) {
        if (b % 2) {
            res = (res * a) % mod;
        }
        b >>= 1;
        a = (a * a) % mod;
    }
    return res % mod;
}

ll c(ll n, ll m) {
    if (m > n / 2) {
        m = n - m;
    }
    ll u, d;
    u = d = 1;
    ll i;
    for (i = 1; i <= m; ++i) {
        d = (d * i) % mod;
        u = (u * (n - i + 1)) % mod;
    }
    return (u * qp(d, mod - 2)) % mod;
}

int main() {
    ll n, a, b;
    cin >> n >> a >> b;
    cout << (2 * mod + qp(2, n) - 1 - c(n, a) - c(n, b)) % mod;
    return 0;
}