Language: C++

#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <numeric>
#include <string>
#include <cstdio>
#include <cstring>
#include <queue>
#include <stack>
#include <set>
#include <cmath>
#include <bitset>

typedef long long ll;
typedef unsigned long long ull;
using namespace std;

#define FALSE printf("false\n");
#define TRUE printf("true\n");
#define all(x) (x).begin(),(x).end()
#define rep(i,n) for(int i = 0;i < ((int)(n));++i)
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define test(a) cout<<"line:"<<__LINE__<<"["<<(#a)<<": "<<(a)<<"]"<<endl

const int INF = 1e9+7;
const ll INFL = 9*1e18;

// const int dx[4] = { 1, 0, -1, 0 };
// const int dy[4] = { 0, 1, 0, -1 };

// const int dx[8] = {1, 1, 0,-1,-1,-1, 0, 1};
// const int dy[8] = {0, 1, 1, 1, 0,-1,-1,-1};

#define SUM(vec) accumulate(all(vec),0LL) // 配列の中身を全部足す
template<typename T>void print(T&& x){cout<<x<<endl;}// 改行付き出力
ll inline digit(ll num){int tmp = 0;while(num){tmp++;num/=10;}return tmp;} // 桁数
template<typename T>inline T digitSum(T num){T sum = 0;while(num){sum+=num%10;num/=10;}return sum;} // 各桁の和
template<typename T>inline T gcd(T a,T b){if(b == 0)return a;return gcd(b,a%b);} // 最大公約数
template<typename T>inline T lcm(T a, T b){T g = gcd(a,b);return a/g*b;} // 最小公倍数
template<typename T>inline T power(T a,T b){T tmp=1;rep(i,b){tmp*=a;}return tmp;} // 累乗
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
int ctoi(char c){return c-'0';}


template<long long MOD>
struct mod_int{
  using ll = long long;
  ll val;
  constexpr mod_int():val(0){}
  constexpr mod_int(ll x)noexcept:val(x>=0?x%MOD:(MOD-(-x)%MOD)%MOD){}
  constexpr ll value()const noexcept{return val;}
  constexpr mod_int operator+(mod_int const& rhs){
    return mod_int(*this)+=rhs;
  }
  constexpr mod_int operator-(mod_int const& rhs){
    return mod_int(*this)-=rhs;
  }
  constexpr mod_int operator*(mod_int const& rhs){
    return mod_int(*this)*=rhs;
  }
  constexpr mod_int operator/(mod_int const& rhs){
    return mod_int(*this)/=rhs;
  }
  constexpr mod_int &operator+=(mod_int const& rhs)noexcept{
    val += rhs.val;
    if(val>=MOD)val-=MOD;
    return *this;
  }
  constexpr mod_int &operator-=(mod_int const& rhs)noexcept{
    if(val<rhs.val)val+=MOD;
    val-=rhs.val;
    return *this;
  }
  constexpr mod_int &operator*=(mod_int const& rhs)noexcept{
    (val*=rhs.val)%=MOD;
    return *this;
  }
  constexpr mod_int &operator/=(mod_int rhs)noexcept{
    *this*=rhs.inverse();
    return *this;
  }
  constexpr bool operator==(mod_int const& rhs)const{
    return val==rhs.val;
  }
  constexpr bool operator!=(mod_int const& rhs)const{
    return !(val==rhs.val);
  }
  constexpr bool operator<(mod_int const& rhs)const{
    return val<rhs.val;
  }
  constexpr bool operator>(mod_int const& rhs)const{
    return val>rhs.val;
  }
  constexpr bool operator<=(mod_int const& rhs)const{
    return !(val>rhs.val);
  }
  constexpr bool operator>=(mod_int const& rhs)const{
    return !(val<rhs.val);
  }
  constexpr friend std::ostream &operator<<(std::ostream& os, mod_int const& mi){
    return os<<mi.val;
  }
  constexpr friend std::istream &operator>>(std::istream& is, mod_int & mi){
    ll t;is>>t;
    mi = mod_int<MOD>(t);
    return is;
  }
  constexpr mod_int inverse(){
    ll a=val,b=MOD,u=1,v=0,t=1;
    while(b>0){
      t=a/b;
      std::swap(a-=t*b,b);
      std::swap(u-=t*v,v);
    }
    return mod_int(u);
  }
  constexpr mod_int mpow(ll n)const{
    mod_int res(1),e(*this);
    while(n){
      if(n&1)res*=e;
      e*=e;
      n>>=1;
    }
    return res;
  }
 
};
using mint = mod_int<1000000007>;
 
mint mpow(ll x,ll n){
  mint res(1),e(x);
  while(n){
    if(n&1)res*=e;
    e*=e;
    n>>=1;
  }
  return res;
}
 
// TODO: write
int main() {
  int n;cin>>n;
  int a,b;cin>>a>>b;
  comb_init();
  if(n == 2){
    print(0);
    return 0;
  }
  mint ans = mpow(2,n)-1;
  mint aKai = 1;
  mint bKai = 1;
  rep(i,a+1)if(i)aKai *= i;
  rep(i,b+1)if(i)bKai *= i;

  mint aTmp = 1;
  rep(i,a)aTmp *= (n-i);
  ans -= aTmp / aKai;
  mint bTmp = 1;
  rep(i,b)bTmp *= (n-i);
  ans -= bTmp/bKai;
  print(ans);
  return 0;
}



Compiler output:
a.cc: In function 'int main()':
a.cc:150:3: error: 'comb_init' was not declared in this scope; did you mean 'mbsinit'?
  150 |   comb_init();
      |   ^~~~~~~~~
      |   mbsinit