#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define mod 1000000007
int ksm(int a, int b) {
    int res = 1;
    while (b) {
        if (b % 2) {
            res = res * a % mod;
        }
        a *= a;
        a %= mod;
        b /= 2;
    }
    return res;
}
int inv(int a) { return ksm(a, mod - 2); }
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, a, b;
    cin >> n >> a >> b;
    int da = 1, db = 1;

    for (int i = 1; i <= a; i++) {
        da *= inv(i);
        da %= mod;
    }
    for (int i = n; i >= n - a + 1; i--) {
        da *= i;
        da %= mod;
    }

    for (int i = 1; i <= b; i++) {
        db *= inv(i);
        db %= mod;
    }
    for (int i = n; i >= n - b + 1; i--) {
        db *= i;
        db %= mod;
    }

    // cout<<da<<" "<<db<<endl;
    int ans = ksm(2, n) - 1 - da - db;
    cout << (ans % mod + mod) % mod << endl;
}