#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL mod = 1e9 + 7;
LL ksm(LL a, LL n) {
    LL ans = 1;
    while (n) {
        if (n & 1)
            ans *= a, ans %= mod;
        a *= a;
        a %= mod;
        n >>= 1;
    }
    return ans;
}
LL jc(LL m) {
    LL ans = 1;
    for (int i = 2; i <= m; i++) {
        ans *= i;
        ans %= mod;
    }
    return ans;
}
LL n, a, b;
int main() {
    scanf("%lld%lld%lld", &n, &a, &b);
    LL ans = ksm(2, n), tmp, tmp2 = 1;

    for (int i = n; i > n - a; i--) tmp2 *= i, tmp2 %= mod;
    tmp = (tmp2 * ksm(jc(a), mod - 2)) % mod;
    ans = (ans - tmp + mod) % mod;

    tmp2 = 1;
    for (int i = n; i > n - b; i--) tmp2 *= i, tmp2 %= mod;
    tmp = (tmp2 * ksm(jc(b), mod - 2)) % mod;
    ans = (ans - tmp + mod) % mod;

    printf("%lld", ans - 1);
    return 0;
}