#define _USE_MATH_DEFINES
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <clocale>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#define IOS ios::sync_with_stdio(false); cin.tie(0);
#define FOR(i, s, n) for(int i = (s), i##_len=(n); i < i##_len; ++i)
#define FORS(i, s, n) for(int i = (s), i##_len=(n); i <= i##_len; ++i)
#define VFOR(i, s, n) for(int i = (s); i < (n); ++i)
#define VFORS(i, s, n) for(int i = (s); i <= (n); ++i)
#define REP(i, n) FOR(i, 0, n)
#define REPS(i, n) FORS(i, 0, n)
#define VREP(i, n) VFOR(i, 0, n)
#define VREPS(i, n) VFORS(i, 0, n)
#define RFOR(i, s, n) for(int i = (s), i##_len=(n); i >= i##_len; --i)
#define RFORS(i, s, n) for(int i = (s), i##_len=(n); i > i##_len; --i)
#define RREP(i, n) RFOR(i, n, 0)
#define RREPS(i, n) RFORS(i, n, 0)
#define ALL(v) (v).begin(), (v).end()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(ALL(v), greater<decltype(v[0])>())
#define SZ(x) ((int)(x).size())
#define REV(x) reverse(ALL(x))
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(ALL(v)), v.end())

using ld = long double;
using ll = long long;
using ui = unsigned int;
using ull = unsigned long long;
using Pi_i = pair<int, int>;
using Pll_ll = pair<ll, ll>;
using VB = vector<bool>;
using VC = vector<char>;
using VD = vector<double>;
using VI = vector<int>;
using VLL = vector<ll>;
using VS = vector<string>;
using VSH = vector<short>;
using VULL = vector<ull>;

const int MOD = 1000000007;
const int INF = 1000000000;
const int NIL = -1;
const double EPS = 1E-10;

template<class T, class S>
bool chmax(T &a, const S &b){
    if(a < b){
        a = b; return true;
    }
    return false;
}
template<class T, class S>
bool chmin(T &a, const S &b){
    if(b < a){
        a = b; return true;
    }
    return false;
}


ll powWithoutMod(ll a, ll b){
    ll ret = 1, aa = a;
    while(b){
        if(b & 1) ret = ret * aa;
        aa *= aa;
        b /= 2;
    }
    return ret;
}

ll power(ll a, ll b, ll m){
    ll ret = 1;
    while(b){
        if(b & 1) ret = (ret * a) % m;
        a = (a * a) % m;
        b /= 2;
    }
    return ret;
}


ll power(ll a, ll b) {
    return power(a, b, MOD);
}

ll inv(int a, ll m){ // GCD(a, m) = 1
    return power(a, m-2);
}

ll inv(int a){
    return inv(a, MOD);
}

int main(){
    int n, a, b;
    cin >> n >> a >> b;
    ll ans = power(2, n) - 1;
    if(ans < 0) ans += MOD;
    VLL INV(max(a, b));
    REP(i, max(a, b)) INV[i] = inv(i+1);
    ll nca = 1, ncb = 1;
    REP(i, a){
        nca = nca * (n-i) % MOD;
        nca = nca * INV[i] % MOD;
    }
    REP(i, b){
        ncb = ncb * (n-i) % MOD;
        ncb = ncb * INV[i] % MOD;
    }
    ans = (ans - nca) % MOD;
    if(ans < 0) ans += MOD;
    ans = (ans - ncb) % MOD;
    if(ans < 0) ans += MOD;
    cout << ans << endl;
    return 0;
}


Measured memory_bytes: 1792