import java.util.*;import java.io.*;import java.math.*;
public class Main
{
    public static void process()throws IOException
    {
        long n=nl();
        long a=nl();
        long b=nl();
        long ans=power(2,n,mod)-1;
        if(ans<0)
            ans+=mod;
        long temp=1;
        for(int i=1;i<=a;i++)
        {
            temp=(temp*(n-i+1))%mod;
            temp=(temp*modInverse(i,mod))%mod;
        }

        ans-=temp;
        if(ans<0)
            ans+=mod;
        temp=1;
        for(int i=1;i<=b;i++)
        {
            temp=(temp*(n-i+1))%mod;
            temp=(temp*(modInverse(i,mod)%mod))%mod;
        }
        ans-=temp;
        if(ans<0)
            ans+=mod;
        pn(ans);
    }

    static AnotherReader sc;
    static PrintWriter out;
    public static void main(String[]args)throws IOException
    {
        boolean oj =true;
        if(oj){sc=new AnotherReader();out=new PrintWriter(System.out);}
        else{sc=new AnotherReader(100);out=new PrintWriter("output.txt");}
        int t=1;
        // t=ni();
        while(t-->0) {process();}
        out.flush();out.close();  
    }


    static long power(long x, long y, long p) 
    { 
        long res = 1; 
        x= x % p;               
        while (y > 0) 
        { 
            if (y % 2 == 1) 
                res = (res * x) % p; 
            y = y >> 1; 
            x = (x * x) % p; 
        } 
        return res; 
    } 
    static long modInverse(long n, long p) 
    { 
        return power(n, p-2, p); 
    } 



    static long mod=(long)1e9+7;
    static void pn(Object o){out.println(o);}
    static void p(Object o){out.print(o);}
    static void pni(Object o){out.println(o);out.flush();}
    static int ni()throws IOException{return sc.nextInt();}
    static long nl()throws IOException{return sc.nextLong();}
    static double nd()throws IOException{return sc.nextDouble();}
    static String nln()throws IOException{return sc.nextLine();}
    static int[] nai(int N)throws IOException{int[]A=new int[N];for(int i=0;i!=N;i++){A[i]=ni();}return A;}
    static long[] nal(int N)throws IOException{long[]A=new long[N];for(int i=0;i!=N;i++){A[i]=nl();}return A;}
    static long gcd(long a, long b)throws IOException{return (b==0)?a:gcd(b,a%b);}
    static int gcd(int a, int b)throws IOException{return (b==0)?a:gcd(b,a%b);}
    static int bit(long n)throws IOException{return (n==0)?0:(1+bit(n&(n-1)));}

/////////////////////////////////////////////////////////////////////////////////////////////////////////

    static class AnotherReader{BufferedReader br; StringTokenizer st;
    AnotherReader()throws FileNotFoundException{
    br=new BufferedReader(new InputStreamReader(System.in));}
    AnotherReader(int a)throws FileNotFoundException{
    br = new BufferedReader(new FileReader("input.txt"));}
    String next()throws IOException{
    while (st == null || !st.hasMoreElements()) {try{
    st = new StringTokenizer(br.readLine());}
    catch (IOException  e){ e.printStackTrace(); }}
    return st.nextToken(); } int nextInt() throws IOException{
    return Integer.parseInt(next());}
    long nextLong() throws IOException
    {return Long.parseLong(next());}
    double nextDouble()throws IOException { return Double.parseDouble(next()); }
    String nextLine() throws IOException{ String str = ""; try{
    str = br.readLine();} catch (IOException e){
    e.printStackTrace();} return str;}}
   
/////////////////////////////////////////////////////////////////////////////////////////////////////////////
}

Measured memory_bytes: 23124