#include <bits/stdc++.h>
using namespace std;
const int p = 1E9 + 7;
int n, a, b;
inline int quick_mul(int a, int b, int x) {
    int rec = 0;
    while (b) {
        if (b & 1)
            rec = (rec % x + a % x) % x;
        a = (a % x + a % x) % x;
        b >>= 1;
    }
    return rec;
}
inline int quick_pow(int a, int b, int x) {
    int rec = 1;
    while (b) {
        if (b & 1)
            rec = quick_mul(rec, a, x);
        a = quick_mul(a, a, x);
        b >>= 1;
    }
    return rec;
}
int C(int n, int m) {
    int fz = 1, fm = 1;
    for (int i = 1; i <= m; ++i) {
        fz = quick_mul(fz, n - i + 1, p);
    }
    for (int i = 1; i <= m; ++i) {
        fm = quick_mul(fm, i, p);
    }
    int inv = quick_pow(fm, p - 2, p);
    return quick_mul(fz, inv, p);
}
int main() {
    scanf("%d %d %d", &n, &a, &b);
    int ans = (quick_pow(2, n, p) - C(n, a) - C(n, b) + 2 * p - 1) % p;
    printf("%d", ans);
}