#include <bits/stdc++.h>
using namespace std;
#define M 1000000007

long long qpow(int x, int n) {
    if (n == 1)
        return x % M;
    else {
        long long tem = qpow(x, n / 2);
        if (n & 1)
            return tem * tem % M * x % M;
        else
            return tem * tem % M;
    }
}

long long C(int n, int a) {
    if (a > n / 2)
        a = n - a;
    if (a == 0)
        return 1;
    long long ans = n;
    for (int i = 1; i < a; ++i) ans = ans * (n - i) % M;
    for (int i = 2; i <= a; ++i) ans = ans * qpow(i, M - 2) % M;
    return ans;
}
int main() {
    int n, a, b;
    cin >> n >> a >> b;
    long long ans = 0;
    ans = qpow(2, n) - 1;
    ans -= C(n, a) + C(n, b);
    while (ans < 0) ans += M;
    ans %= M;
    cout << ans;
    return 0;
}