using System;
using static System.Console;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;

class Program
{
    private const int mod = 1000000007;

    static void Main()
    {
        var input = MyUtil.ReadintArray();
        Modular res = Modular.Pow(2, input[0]) - 1;

        res -= Combination(input[0], input[1]);
        res -= Combination(input[0], input[2]);

        WriteLine((int)res);
        ReadKey();
    }

    static Modular Combination(int a, int b)
    {
        Modular n = 1;
        Modular c = 1;

        for (int i = 0; i < b; i++)
        {
            n *= (a - i);
            c *= (i + 1);
        }

        Modular res = n * Modular.Pow(c, mod - 2);
        return res;
    }
}

class Modular
{
    private const int M = 1000000007;
    private long value;
    public Modular(long value) { this.value = value; }
    public static implicit operator Modular(long a)
    {
        var m = a % M;
        return new Modular((m < 0) ? m + M : m);
    }
    public static Modular operator +(Modular a, Modular b)
    {
        return a.value + b.value;
    }
    public static Modular operator -(Modular a, Modular b)
    {
        return a.value - b.value;
    }
    public static Modular operator *(Modular a, Modular b)
    {
        return a.value * b.value;
    }
    public static Modular Pow(Modular a, int n)
    {
        switch (n)
        {
            case 0:
                return 1;
            case 1:
                return a;
            default:
                var p = Pow(a, n / 2);
                return p * p * Pow(a, n % 2);
        }
    }
    public static Modular operator /(Modular a, Modular b)
    {
        return a * Pow(b, M - 2);
    }
    private static readonly List<int> facs = new List<int> { 1 };
    private static Modular Fac(int n)
    {
        for (int i = facs.Count; i <= n; ++i)
        {
            facs.Add((int)(Math.BigMul(facs.Last(), i) % M));
        }
        return facs[n];
    }
    public static Modular Ncr(int n, int r)
    {
        return (n < r) ? 0
             : (n == r) ? 1
                        : Fac(n) / (Fac(r) * Fac(n - r));
    }
    public static explicit operator int(Modular a)
    {
        return (int)a.value;
    }
}


static class MyUtil
{
    /// <summary>
    /// 指定の桁のビットを取得します。
    /// </summary>
    /// <param name="num"></param>
    /// <param name="count">取得する桁。</param>
    /// <returns></returns>
    public static int GetBit(this int num, int count)
    {
        int mask = (int)Math.Pow(2, count - 1);
        return (num & mask) == 0 ? 0 : 1;
    }

    /// <summary>
    /// <c>int</c>を2進数ビット配列に変換します。
    /// </summary>
    /// <param name="num"></param>
    /// <returns></returns>
    public static int[] ToBitArray(this int num)
    {
        const int size = sizeof(int) * 8;
        var array = new int[size];
        for (int i = 0; i < size; i++)
        {
            array[i] = num.GetBit(size - i);
        }
        return array;
    }

    public static long[] ReadlongArray()
    {
        return ReadLine().Split(' ').Select(s => long.Parse(s)).ToArray();
    }

    public static int[] ReadintArray()
    {
        return ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
    }

    /// <summary>
    /// <see cref="IEnumerable{T}"/>の各要素を並べてコンソールに出力します。各要素の間には半角スペースが一つ入ります。
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="ts"></param>
    public static void WriteToConsole<T>(this IEnumerable<T> ts)
    {
        StringBuilder stringBuilder = new StringBuilder();
        foreach (T t in ts)
        {
            stringBuilder.Append(t.ToString());
            stringBuilder.Append(" ");
        }
        stringBuilder.Remove(stringBuilder.Length - 1, 1);
        Console.WriteLine(stringBuilder.ToString());
    }

    public static void WriteToDebugConsole<T>(this IEnumerable<T> ts)
    {
        StringBuilder stringBuilder = new StringBuilder();
        foreach (T t in ts)
        {
            stringBuilder.Append(t.ToString());
            stringBuilder.Append(" ");
        }
        stringBuilder.Remove(stringBuilder.Length - 1, 1);
        System.Diagnostics.Debug.WriteLine(stringBuilder.ToString());
    }
}


Measured memory_bytes: 17484