#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using Pi = pair<int, int>;
using Pl = pair<ll, ll>;
using vint = vector<int>;
using vvint = vector<vint>;
using vvvint = vector<vvint>;
using vll = vector<ll>;
using uint = unsigned int;
using ull = unsigned long long;

template<typename T> using uset = unordered_set<T>;
template<typename T1, typename T2> using umap = unordered_map<T1, T2>;

constexpr int INF = (1 << 30) - 1;
constexpr ll LLINF = 1LL << 60;
constexpr int dy[] = {1, 0, -1, 0, 1, -1, -1, 1};
constexpr int dx[] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr char el = '\n';
constexpr int mod = 1000000007;

template<typename T> T gcd(T a, T b) { return (b ? gcd(b, a % b) : a); }
template<typename T> T lcm(T a, T b) { return (a / gcd(a, b) * b); }
template<typename T1, typename T2> inline void chmin(T1 &a, T2 b) { if (a > b) a = b; }
template<typename T1, typename T2> inline void chmax(T1 &a, T2 b) { if (a < b) a = b; }

template<typename T>
ostream& operator <<(ostream &os, vector<T> &v) {
	for (auto &u : v) os << u << el;
	return (os);
}

template<typename T>
istream& operator >>(istream &is, vector<T> &v) {
	for (auto &u : v) is >> u;
	return (is);
}

template<typename T1, typename T2>
istream& operator >>(istream &is, pair<T1, T2> &p) {
	return (is >> p.first >> p.second);
}

template < unsigned MOD >
class Modint {
	public:
		using uint = unsigned;
		using u64 = uint64_t;
		using i64 = int64_t;

		Modint (const i64 dat = 0) : dat(dat >= 0 ? dat % MOD : (MOD - (-dat) % MOD) % MOD) {}

		constexpr Modint operator + (const Modint &v) const { return ( Modint(dat + v.dat) ); }
		constexpr Modint operator - () const { return ( Modint(-((i64)dat)) ); }
		constexpr Modint operator - (const Modint &v) const { return ( (*this) + -v ); }
		constexpr Modint operator * (const Modint &v) const { return ( Modint((u64)dat * v.dat) ); }

		constexpr Modint operator ~ () const {
			i64 a = dat, b = MOD, x1 = 1, x2 = 0, t;

			while ( b > 0 ) {
				t = a / b;
				swap(a -= t * b, b);
				swap(x1 -= t * x2, x2);
			}

			return ( Modint(x1) );
		}

		constexpr Modint operator / (const Modint &v) const { return ( (*this) * ~v ); }

		Modint &operator = (const i64 &v) { return ( (*this) = Modint < MOD > (v) ); }
		Modint &operator += (const Modint &v) { return ( (*this) = (*this) + v ); }
		Modint &operator -= (const Modint &v) { return ( (*this) = (*this) - v ); }
		Modint &operator *= (const Modint &v) { return ( (*this) = (*this) * v ); }
		Modint &operator /= (const Modint &v) { return ( (*this) = (*this) / v ); }

		constexpr Modint operator ^ (u64 n) const {
			Modint < MOD > ret(1), mul(dat);
			while ( n > 0 ) {
				if ( n & 1 ) ret *= mul;
				mul *= mul;
				n >>= 1;
			}
			return ( ret );
		}

		bool operator == (const Modint &v) { return ( dat == v.dat ); }
		bool operator != (const Modint &v) { return ( dat != v.dat ); }

		friend ostream& operator << (ostream &os, const Modint &p ) {
			return ( os << p.dat );
		}

		friend istream& operator >> (istream &is, Modint &p ) {
			i64 data;
			is >> data;
			p = Modint < MOD >(data);
			return ( is );
		}

	private:
		uint dat;
};

int main() {
	ll N; cin >> N;
	ll a, b; cin >> a >> b;
	
	Modint<mod> beki = 2;
	Modint<mod> ans = (beki^N) - 1;
	
	Modint<mod> dat = 1;
	for (int i = 1; i <= max(a, b); i++) {
		dat *= (N-i+1);
		dat /= i;
		if (i == a || i == b) ans -= dat;
	}
	cout << ans << endl;
	return (0);
}


Measured memory_bytes: 256