using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using static System.Console;
using static System.Math;
using static MyIO;
using static MyUtil;

public class D
{
	public static void Main() => (new Solver()).Solve();
}

public class Solver
{
	public void Solve()
	{
		long n = GetLong();
		long a = GetLong();
		long b = GetLong();

		var all = ModInt.ModPow(new ModInt(2), new ModInt(n));
		WriteLine(((all - 1) - comb(n, a) - comb(n, b)).Val);
	}

	private ModInt comb(long n, long x)
	{
		var res = new ModInt(1);
		for(long i = 0; i < x; i++)
			res *= (n - i);

		for(long i = x; i > 0; i--)
			res /= i;

		return res;
	}
}

public struct ModInt
{
	public long Mod { get; private set; }
	public long Val { get; private set; }

	public ModInt(long v)
	{
		Mod = 1000000007;  // must initialize
		Val = (v + Mod) % Mod;
	}

	public static ModInt operator+(ModInt x, ModInt y)
	{
		long mod = x.Mod;
		long tmp = x.Val + y.Val;
		if(tmp >= mod)
			tmp -= mod;
		return new ModInt(tmp);
	}

	public static ModInt operator-(ModInt x, ModInt y)
	{
		long mod = x.Mod;
		long tmp = x.Val;
		if(tmp < y.Val)
			tmp += mod;
		tmp -= y.Val;
		return new ModInt(tmp);
	}

	public static ModInt operator*(ModInt x, ModInt y)
	{
		long mod = x.Mod;
		return new ModInt((x.Val * y.Val) % mod);
	}

	public static ModInt operator/(ModInt x, ModInt y)
	{
		long mod = x.Mod;
		return x * ModPow(y, mod - 2);
	}

	public static ModInt ModPow(ModInt x, ModInt y)
	{
		long mod = x.Mod;
		long exp = y.Val;
		long xx = x.Val;
		long res = 1;
		while(exp > 0)
		{
			if((exp & 1) == 1)
				res = (res * xx) % mod;

			xx = (xx * xx) % mod;
			exp >>= 1;
		}
		return new ModInt(res);
	}

	public static ModInt operator+(ModInt x, long y) => x + new ModInt(y);
	public static ModInt operator-(ModInt x, long y) => x - new ModInt(y);
	public static ModInt operator*(ModInt x, long y) => x * new ModInt(y);
	public static ModInt operator/(ModInt x, long y) => x / new ModInt(y);
	public static ModInt operator+(long x, ModInt y) => new ModInt(x) + y;
	public static ModInt operator-(long x, ModInt y) => new ModInt(x) - y;
	public static ModInt operator*(long x, ModInt y) => new ModInt(x) * y;
	public static ModInt operator/(long x, ModInt y) => new ModInt(x) / y;
	public static ModInt ModPow(long x, ModInt y) => ModPow(new ModInt(x), y);
	public static ModInt ModPow(ModInt x, long y) => ModPow(x, new ModInt(y));
}

public static class MyIO
{
	private static string[] args = null;
	private static int num = -1;
	private static int used = -1;

	private static string getArg()
	{
		if(used == num)
		{
			args = Console.ReadLine().Split(' ');
			num = args.Length;
			used = 0;
		}
		return args[used++];
	}

	public static int GetInt() => int.Parse(getArg());
	public static long GetLong() => long.Parse(getArg());
	public static double GetDouble() => double.Parse(getArg());
	public static decimal GetDecimal() => decimal.Parse(getArg());
	public static string GetString() => getArg();
	public static char GetChar() => getArg()[0];
	public static int[] GetInts(long N) => Enumerable.Range(0, (int)N).Select(_ => GetInt()).ToArray();
	public static long[] GetLongs(long N) => Enumerable.Range(0, (int)N).Select(_ => GetLong()).ToArray();
	public static double[] GetDoubles(long N) => Enumerable.Range(0, (int)N).Select(_ => GetDouble()).ToArray();
	public static decimal[] GetDecimals(long N) => Enumerable.Range(0, (int)N).Select(_ => GetDecimal()).ToArray();
	public static string[] GetStrings(long N) => Enumerable.Range(0, (int)N).Select(_ => GetString()).ToArray();
}

public static class MyUtil
{
	public static void chmax<T>(ref T x, T y) where T : IComparable<T>
	{
		if(x.CompareTo(y) < 0)
			x = y;
	}

	public static void chmin<T>(ref T x, T y) where T : IComparable<T>
	{
		if(x.CompareTo(y) > 0)
			x = y;
	}

	public static void swap<T>(ref T x, ref T y)
	{
		T tmp = x;
		x = y;
		y = tmp;
	}
}

Measured memory_bytes: 11220