#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <cmath>
#include <functional>
#include <iomanip>

using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vi>;

// #define rep(i,n) for(int i=0;i<(n);++i)
#define all(f,c,...) (([&](decltype((c)) cccc) { return (f)(begin(cccc), end(cccc), ## __VA_ARGS__); })(c))
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) for(int i=0;i<(n);++i)
#define repi(i,a,b) for(int i=(a);i<(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define _fromto2(i,n) for(int i=0;i<=(n);++i)
#define _fromto3(i,a,b) for(int i=(a);i<=(b);++i)
#define fromto(...) _overload3(__VA_ARGS__,_fromto3,_fromto2,)(__VA_ARGS__)

#define rrep(i,n) for(int i=(n);i>=0;--i)
const int MOD = 1e9+7;
const int INF = 1e9;
const int dx[4]={1,0,-1,0}, dy[4]={0,1,0,-1};
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return 1;}return 0;}

// debug
template<class T>ostream& operator<<(ostream& os,const vector<T>& vec){os<<"{";for(int i=0;i<vec.size();++i)os<<(i?", ":"")<<vec[i];os<<"}";return os;}
template<class T1,class T2>ostream& operator<<(ostream& os,const pair<T1,T2>& rhs){os<<"("<<rhs.first<<", "<<rhs.second<<")";return os;}

#ifdef LOCAL
void debug() {cerr << "\n";}
template<class First> void debug(const First& first) {cerr<<first<<"\n";}
template<class First, class... Rest> void debug(const First& first, const Rest&... rest) {cerr<<first<<",";debug(rest...);}
#else
#define debug(...) 42
#endif


template<int MOD> struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) { if (val < 0) val += MOD; }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator - () const noexcept { return val ? MOD - val : 0; }
    constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator += (const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator -= (const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator *= (const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator /= (const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator == (const Fp& r) const noexcept { return this->val == r.val; }
    constexpr bool operator != (const Fp& r) const noexcept { return this->val != r.val; }
    friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept { return os << x.val; }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};

using mint = Fp<MOD>;

int main() {
  int N, a, b; cin >> N >> a >> b;

  mint ans = modpow((mint)2, N) - 1;

  mint combination = 1;
  rep(i, max(a, b)) {
    combination *= (N-i);
    combination /= i+1;
    if (i + 1 == a || i + 1 == b)
      ans -= combination;
  }
  cout << ans << endl;

// nCi = n! / (k!(n-k)!)


  return 0;
}


Measured memory_bytes: 256