#include<bits/stdc++.h>
using namespace std;
const long long md=1e9+7;
long long n,pw=2,ans=1,a,b,jj=1,nd;
long long pww(long long x,long long y)
{
	nd=1;
	while(x)
	{
		if(x%2==1)
		{
			nd*=y;
			nd%=md;
		}
		y*=y;
		y%=md;
		x/=2;
	}
	return nd;
}
int main()
{
	cin>>n>>a>>b;
	ans=pww(n,2);
	jj=1;
	for(long long i=n;i>=n-a+1;i--)
	{
		jj*=i;
		jj%=md;
	}
	for(long long i=1;i<=a;i++)
	{
		jj*=pww(md-2,i);
		jj%=md;
	}
	ans=(ans-jj+md)%md;
	jj=1;
	for(long long i=n;i>=n-b+1;i--)
	{
		jj*=i;
		jj%=md;
	}
	for(long long i=1;i<=b;i++)
	{
		jj*=pww(md-2,i);
		jj%=md;
	}
	ans=(ans-jj+md)%md;
	cout<<(ans-1+md)%md<<endl;
	return 0;
}