#include<bits/stdc++.h>
#define D(x) cerr<<#x<<'='<<x<<'\n';
using namespace std;
typedef long long ll;
const ll P=1000000007;
ll ksm(ll x,ll y)
{
	ll ret=1;
	while (y)
	{
		if (y&1)
			ret=ret*x%P;
		x=x*x%P;
		y>>=1;
	}
	return ret;
}
ll C(ll x,ll y)
{
	ll ret=1;
	for (ll i=x;i>=x-y+1;i--)
		ret=ret*i%P;
	for (ll i=1;i<=y;i++)
		ret=ret*ksm(i,P-2)%P;
	return ret;
}
int main()
{
	ll n,a,b;
	scanf("%lld%lld%lld",&n,&a,&b);
	ll ans=(ksm(2,n)-1-C(n,a)-C(n,b)+3*P)%P;
	printf("%lld",ans);
	return 0;
}