/*by freesteed*/
#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define pb push_back
#define fill(x,c) memset(x,c,sizeof(x))
#define fi first
#define se second
#define sz(A) (int)(A.size())
#define all(x) (x).begin(),(x).end()
#define caset int ___T; cin>>___T; for(int cs=1;cs<=___T;cs++)
typedef long long ll;
typedef pair<int,int> PII;
typedef vector<int> VI;
const ll mod=1e9+7;
const ll oo=1e9+10;
const int Max = 1e6+10;
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
int ri() {
	int n;
	scanf("%d", &n);
	return n;
}
int64_t rs64() {
	int64_t n;
	scanf("%" SCNd64, &n);
	return n;
}
#define MOD 1000000007
template<int mod>
struct ModInt{
	int x;
	ModInt():x(0){}
	ModInt(long long y):x(y>=0?y%mod:(mod-(-y)%mod)%mod){}
	ModInt &operator+=(const ModInt &p){
		if((x+=p.x)>=mod)x-=mod;
		return *this;
	}
	ModInt &operator-=(const ModInt &p){
		if((x+=mod-p.x)>=mod)x-=mod;
		return *this;
	}
	ModInt &operator*=(const ModInt &p){
		x=(int)(1LL*x*p.x%mod);
		return *this;
	}
	ModInt &operator/=(const ModInt &p){
		*this*=p.inverse();
		return *this;
	}
	ModInt &operator^=(long long p){
		ModInt res = 1;
		for (; p; p >>= 1) {
			if (p & 1) res *= *this;
			*this *= *this;
		}
		return *this = res;
	}
	ModInt operator-()const{return ModInt(-x);}
	ModInt operator+(const ModInt &p)const{return ModInt(*this)+=p;}
	ModInt operator-(const ModInt &p)const{return ModInt(*this)-=p;}
	ModInt operator*(const ModInt &p)const{return ModInt(*this)*=p;}
	ModInt operator/(const ModInt &p)const{return ModInt(*this)/=p;}
	ModInt operator^(long long p)const{return ModInt(*this)^=p;}
	bool operator==(const ModInt &p)const{return x==p.x;}
	bool operator!=(const ModInt &p)const{return x!=p.x;}
	explicit operator int() const { return x; }						   // added by QCFium
	ModInt operator=(const int p) {x = p; return ModInt(*this);} // added by QCFium
	ModInt inverse()const{
		int a=x,b=mod,u=1,v=0,t;
		while(b>0){
			t=a/b;
			a-=t*b;
			std::swap(a,b);
			u-=t*v;
			std::swap(u,v);
		}
		return ModInt(u);
	}
	friend std::ostream &operator<<(std::ostream &os,const ModInt<mod> &p){
		return os<<p.x;
	}
	friend std::istream &operator>>(std::istream &is,ModInt<mod> &a){
		long long x;
		is>>x;
		a=ModInt<mod>(x);
		return (is);
	}
};
typedef ModInt<MOD> mint;

struct MComb {
	std::vector<mint> fact;
	std::vector<mint> inversed;
	MComb(int n) { // O(n+log(mod))
		fact = std::vector<mint>(n+1,1);
		for (int i = 1; i <= n; i++) fact[i] = fact[i-1]*mint(i);
		inversed = std::vector<mint>(n+1);
		inversed[n] = fact[n] ^ (MOD-2);
		for (int i = n - 1; i >= 0; i--) inversed[i]=inversed[i+1]*mint(i+1);
	}
	mint ncr(int n, int r) {
		return (fact[n] * inversed[r] * inversed[n-r]);
	}
	mint npr(int n, int r) {
		return (fact[n] * inversed[n-r]);
	}
	mint nhr(int n, int r) {
		assert(n+r-1 < (int)fact.size());
		return ncr(n+r-1, r);
	}
};
mint ncr(int n, int r) {
	mint res = 1;
	for (int i = n - r + 1; i <= n; i++) res *= i;
	for (int i = 1; i <= r; i++) res /= i;
	return res;
}
int help() {
	int n = ri();
	int a = ri();
	int b = ri();
	//MComb com(n);
	mint res = (mint(2) ^ n) - 1 - ncr(n, a) - ncr(n, b);
	std::cout << res << std::endl;
	return 0;
}
//ll a[Max];
void solve(){
	help(); 
}
int main() {
	ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	//caset{
		solve();
	//}
  	return 0;
}





Measured memory_bytes: 256