// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define range(i,a,b) ((a)<=(i) && (i)<(b))
#define debug(x) cout << #x << ' ' << '=' << ' ' << (x) << endl;
#define fs first
#define sc second
#define pb push_back
typedef long long ll;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> T;
typedef priority_queue<ll> PQI;
typedef priority_queue<P> PQP;
typedef vector<vector<P>> pvec;
typedef vector<vector<ll>> vvec;
typedef vector<ll> vec;
const vector<int> dx = {0, -1, 0, 1, 1, 1, -1, -1};
const vector<int> dy = {1, 0, -1, 0, 1, -1, 1, -1};
const int MOD = (1000000007);
// const int MOD = (998244353);
// const int INF = (1 << 30);
const int INF = (1LL << 60);
const double EPS = (1 >> 30);
template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return 1;} return 0;}
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return 1;} return 0;}

int gcd(int x, int y) { return y ? gcd(y, x%y) : x; }
int lcm(int x, int y) { return x/gcd(x, y)*y; }
int mod_pow(int x, int y) { int res = 1; while (y > 0) { if (y & 1) { res = res * x % MOD; } x = x * x % MOD; y >>= 1; } return res; }
int comb(int n, int k) { k = min(k, n - k); int nnn = 1; for (int i = n - k + 1; i <= n; i++) { nnn *= i; nnn %= MOD; } int kkk = 1; for (int i = 1; i <= k; i++) { kkk *= i; kkk %= MOD; } return (nnn * mod_pow(kkk, MOD - 2)) % MOD; }
int to_int(string s) { int n = s.size(); int ans = 0; for (int i = 0; i < n; i++) { ans = ((ans * 10) + (s[i] - '0')) % MOD; } return ans; }
bool is_prime(int n) { for(int i = 2; i*i <= n; i++) { if (n % i == 0) return false; } return n != 1; }
int extgcd(int a, int b, int& x, int& y) { // ax+by = gcd(a,b) >> gcd(a, b)
    int d = a;
    if(d != 0) { d = extgcd(b, a%b, y, x); y -= (a/b)*x; }
    else { x = 1, y = 0; }
    return 0;
}

#include <cstdint>
 
template <long long Modulus> class modint {
  long long a;
 
public:
    constexpr modint(const long long x = 0) noexcept : a((x % Modulus + Modulus) % Modulus) {}
    constexpr long long val() const noexcept { 
        return a; 
    }
    constexpr modint operator + (const modint rhs) const noexcept {
        return modint(*this) += rhs;
    }
    constexpr modint operator - (const modint rhs) const noexcept {
        return modint(*this) -= rhs;
    }
    constexpr modint operator * (const modint rhs) const noexcept {
        return modint(*this) *= rhs;
    }
    constexpr modint operator / (const modint rhs) const noexcept {
        return modint(*this) /= rhs;
    }
    constexpr modint &operator += (const modint rhs) noexcept {
        a += rhs.a;
        if (a >= Modulus) {
            a -= Modulus;
        }
        return *this;
    }
    constexpr modint &operator -= (const modint rhs) noexcept {
        if (a < rhs.a) {
            a += Modulus;
        }
        a -= rhs.a;
        return *this;
    }
    constexpr modint &operator *= (const modint rhs) noexcept {
        a = a * rhs.a % Modulus;
        return *this;
    }
    constexpr modint &operator /= (modint rhs) noexcept {
        long long exp = Modulus - 2;
        while (exp) {
          if (exp % 2) {
              *this *= rhs;
          }
          rhs *= rhs;
          exp /= 2;
      }
      return *this;
    }
    constexpr bool operator == (const modint rhs) const noexcept {
        return modint(*this).val() == rhs.val();
    }
    constexpr bool operator != (const modint rhs) const noexcept {
        return modint(*this).val() != rhs.val();
    }
};
using mint = modint<MOD>;
typedef vector<mint> mvec;
typedef vector<vector<mint>> mvvec;
 
// 二項係数ライブラリ
template<class T> struct BC {
    vector<T> fact_, inv_, finv_;
    constexpr BC() {}
    constexpr BC(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) {
        init(n);
    }
    constexpr void init(int n) noexcept {
        fact_.assign(n, 1);
        inv_.assign(n, 1);
        finv_.assign(n, 1);
        for(int i = 2; i < n; i++){
            fact_[i] = fact_[i-1] * i;
            inv_[i] = inv_[MOD%i] * (MOD/i) * (-1);
            finv_[i] = finv_[i-1] * inv_[i];
        }
    }
    constexpr T nCr(int n, int k) const noexcept {
        if (n < k || n < 0 || k < 0) return 0;
        return fact_[n] * finv_[k] * finv_[n-k];
    }
    constexpr T nPr(int n, int k) const noexcept {
        if (n < k || n < 0 || k < 0) return 0;
        return fact_[n] * finv_[n-k];
    }
    constexpr T nHr(int n, int k) const noexcept {
        return nCr(n + k - 1, k);
    }
    constexpr T fact(int n) const noexcept {
        if (n < 0) return 0;
        return fact_[n];
    }
    constexpr T inv(int n) const noexcept {
        if (n < 0) return 0;
        return inv_[n];
    }
    constexpr T finv(int n) const noexcept {
        if (n < 0) return 0;
        return finv_[n];
    }
};
 
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);
    //---------------------------------------------
    
    int n,a,b;
    cin>>n>>a>>b;
    mint ans=mod_pow(2,n)-1;
    ans-=comb(n,a);
    ans-=comb(n,b);
    cout<<ans.val()<<endl;


    
}

Measured memory_bytes: 256