#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <math.h>

long long Powmod(long long x, long long y, long int mod);  //(x^y)%mod

int main() {
    long int n;
    long long sum;
    int a, b;
    scanf("%ld%d%d", &n, &a, &b);
    long int temp = 1000000007;
    sum = Powmod(2, n, temp);
    sum--;
    long long k = 1, kr = 1;
    for (int i = 0; i < a; i++) {
        k = (k * (n - i)) % temp;
        kr = (kr * (i + 1)) % temp;
    }
    k = k * Powmod(kr, temp - 2, temp) % temp;
    sum -= k;
    k = 1;
    kr = 1;
    for (int i = 0; i < b; i++) {
        k = (k * (n - i)) % temp;
        kr = (kr * (i + 1)) % temp;
    }
    k = k * Powmod(kr, temp - 2, temp) % temp;
    sum -= k;
    while (sum < 0) {
        sum += temp;
    }
    printf("%lld", sum);
    return 0;
}

long long Powmod(long long x, long long y, long int mod) {
    long long b = y, ans = 1;
    x = x % mod;
    while (b > 0) {
        if (b % 2 == 1) {
            ans = ans * x % mod;
        }
        x = x * x % mod;
        b /= 2;
    }
    return ans;
}