#include <cstdio>
using namespace std;

int n, a, b;
int p = 1e9 + 7;
char ch;
inline void read(int &x) {
    x = 0;
    for (ch = getchar(); ch < '0' || ch > '9'; ch = getchar())
        ;
    for (; ch >= '0' && ch <= '9'; ch = getchar()) {
        x = (x << 3) + (x << 1) + (ch & 15);
    }
}

int quick_pow(int x, int m) {
    int ans = 1;
    while (m > 0) {
        if (m & 1)
            ans = 1ll * ans * x % p;
        x = 1ll * x * x % p;
        m = m >> 1;
    }
    return ans;
}
int c(int a, int b) {
    int ans = 1, x = 1;
    for (int i = a - b + 1; i <= a; i++) ans = 1ll * ans * i % p;
    for (int i = 1; i <= b; i++) x = 1ll * x * i % p;
    return 1ll * ans * quick_pow(x, p - 2) % p;
}

int main() {
    read(n);
    read(a);
    read(b);
    printf("%d", ((quick_pow(2, n) - c(n, a) - c(n, b) - 1) % p + p) % p);
    return 0;
}