#include <stdio.h>
#define MAX 1000000007
long int mul(long int a, long int b, long int m) {
    int r = 0;
    while (b) {
        if (b & 1)
            r = (r + a) % m;
        a = a * 2 % m;
        b >>= 1;
    }
    return r;
}
long int pow(long int a, long int b, long int m) {
    long int r = 1;
    while (b) {
        if (b & 1)
            r = mul(r, a, m);
        a = mul(a, a, m);
        b >>= 1;
    }
    return r;
}
long int C(long int n, long int x) {
    if (x > n / 2)
        x = n - x;
    long int sum1 = 1;
    long int sum2 = 1;
    for (int i = 0; i < x; i++) {
        sum1 = mul(sum1, n - i, MAX);
        sum2 = mul(sum2, i + 1, MAX);
    }
    long int tmp = pow(sum2, MAX - 2, MAX);
    return mul(sum1, tmp, MAX);
}
int main() {
    long int n, a, b;
    scanf("%ld%ld%ld", &n, &a, &b);
    long int sum = pow(2, n, MAX);
    // printf("%ld\n",sum);
    long int ans1 = (sum - C(n, a) - C(n, b) + 2 * MAX - 1) % MAX;
    // printf("%ld\n",ans1);
    printf("%ld", ans1);
    return 0;
}