import java.io.*;
import java.util.StringTokenizer;

public class Main {
    public static Reader in;
    public static PrintWriter out;
    public static void main(String[] args) {
        out = new PrintWriter(new BufferedOutputStream(System.out));
        in = new Reader();
        int t = 1;
        while (t-- > 0) solve();
        out.close();
    }
    static int mod = (int) 1e9 + 7;
    static long[] fac, inv;
    static void solve() {
        int n = in.nextInt(), a = in.nextInt(), b = in.nextInt();
        long re = -1l + qmi(2, n, mod) - C(n, a, mod) - C(n, b, mod) + mod * 3l;
        out.println(re % mod);
    }
    static long C(int a, int b, int p) {
        long fa = 1l, fb = 1l;
        for (int i = 1; i <= b; i++) {
            fa = (fa * (a + 1 - i)) % p;
            fb = (fb * i) % p;
        }
        return fa * qmi(fb, p - 2, p) % mod;
    }
    static int qmi(long a, int b, int p) {
        long ans = 1;
        a = (a % p + p) % p;
        for (; b > 0; b >>= 1) {
            if ((b & 1) != 0)
                ans = (a * ans) % p;
            a = (a * a) % p;
        }
        return (int) ans;
    }

    static class Reader {
        private BufferedReader br;
        private StringTokenizer st;

        Reader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            try {
                while (st == null || !st.hasMoreTokens()) {
                    st = new StringTokenizer(br.readLine());
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] nextIntArray(int n) {
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) arr[i] = nextInt();
            return arr;
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        String nextLine() {
            String s = "";
            try {
                s = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return s;
        }
    }
}