#include <algorithm>
#include <boost/optional.hpp>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iostream>
#include <limits>
#include <list>
#include <numeric>
#include <queue>
#include <sstream>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>
#include <vector>

#define REP(i, n) for(int i = 0, i##_MACRO = (n); i < i##_MACRO; i++)
#define RANGE(i, a, b) for(int i = (a), i##_MACRO = (b); i < i##_MACRO; i++)
#define EACH(e, a) for(auto&& e : a)
#define ALL(a) (a).begin(), (a).end()
#define AALL(a, n) (a), ((a) + (n))
#define FILL(a, n) memset((a), n, sizeof(a))
#define FILLZ(a) FILL(a, 0)

using namespace std;

using ll = long long;
using VI = vector<int>;
using VI2D = vector<vector<int>>;

const int INF = 2e9;
const double EPS = 1e-10;
const double PI = acos(-1.0);

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};

template <typename T>
int sign(T x) {
	return x < 0 ? -1 : x > 0 ? 1 : 0;
}

template <>
int sign(double x) {
	return x < -EPS ? -1 : x > EPS ? 1 : 0;
}

template <typename T>
void chmax(T& m, T x) {
	m = max(m, x);
}

template <typename T>
void chmin(T& m, T x) {
	m = min(m, x);
}

template <typename T>
T square(T x) {
	return x * x;
}

inline int toInt(string s) {
	int v;
	istringstream sin(s);
	sin >> v;
	return v;
}

template <long long MOD = 1000000007>
class ModInt {
	public:
	long long n;

	ModInt() : n(0) {}
	ModInt(long long n) : n(n) {
		while(n < 0) {
			this->n += MOD;
		}
		this->n %= MOD;
	}

	long long get() { return this->n; }
	long long get_mod() { return MOD; }

	static ModInt pow(ModInt a, long long n) {
		ModInt ret(1LL);
		while(n != 0) {
			if(n % 2) {
				ret *= a;
			}
			a *= a;
			n /= 2;
		}
		return ModInt(ret);
	}
	ModInt pow(long long n) { return ModInt<MOD>::pow(*this, n); }
	ModInt inv() const { return ModInt<MOD>::pow(*this, MOD - 2); }

	ModInt& operator+=(const ModInt rhs) {
		this->n += rhs.n;
		this->n %= MOD;
		return *this;
	}
	ModInt& operator-=(const ModInt rhs) {
		if((this->n -= rhs.n) < 0) {
			this->n += MOD;
		}
		return *this;
	}
	ModInt& operator*=(const ModInt rhs) {
		this->n *= rhs.n;
		this->n %= MOD;
		return *this;
	}
	ModInt& operator/=(const ModInt rhs) {
		*this *= rhs.inv();
		return *this;
	}
	ModInt operator+(const ModInt rhs) { return ModInt(*this) += rhs; }
	ModInt operator-(const ModInt rhs) { return ModInt(*this) -= rhs; }
	ModInt operator*(const ModInt rhs) { return ModInt(*this) *= rhs; }
	ModInt operator/(const ModInt rhs) { return ModInt(*this) /= rhs; }
};
ostream& operator<<(ostream& os, ModInt<> x) {
	return os << x.n;
}
istream& operator>>(istream& is, ModInt<>& x) {
	return is >> x.n;
}

// modの逆元
long long mod_inv(long long n, long long mod) {
	return ModInt<>::pow(n, mod - 2).n;
}

template <long long MOD = 1000000007>
ModInt<MOD> mod_comb(long long n, long long r) {
	ModInt<MOD> ret(1);
	r = std::min(r, n - r);
	for(int i = 0; i < r; i++) {
		ret *= (n - i);
		ret /= i + 1;
	}
	return ret;
}

int main() {
	int n, a, b;
	scanf("%d %d %d", &n, &a, &b);
	ModInt<> all = ModInt<>(2).pow(n) - 1;
	cout << all - mod_comb<>(n, a) - mod_comb<>(n, b) << endl;
	return 0;
}

Measured memory_bytes: 256