Go: package main

import "fmt"

func main() {
	//部屋を生成
	var H int

	fmt.Scan(&H)
	room := [][4]bool{}

	for i := 0; i < H; i++ {
		room = append(room, [4]bool{})
	}

	//荷物のおけない区画を設定
	var N int
	fmt.Scan(&N)
	for i := 0; i < N; i++ {
		var x, y int
		fmt.Scan(&x, &y)
		room[y][x] = true //ものがある状態を真とする
	}
	//荷物を配置
	var count int
	for j := 0; j < H-1; j++ {
		for i := 0; i < 3; i++ {

			if !room[j][i] && !room[j+1][i] && !room[j][i+1] && !room[j+1][i+1] {
				//if i!=0&&i!=2&&j!=H-3{
				//	if !room[j+1][i-1]&&!room[j+1][i+2]{
				//		if !room[j+2][0]&&!room[j+2][1]&&!room[j+2][2]&&!room[j+2][3]{
				//			break
				//		}
				//	}
				//}
				room[j][i] = true
				room[j+1][i] = true
				room[j][i+1] = true
				room[j+1][i+1] = true
				count++
			}
		}
	}
	//for _,v:=range room{
	//	for _,v2:=range v{
	//		if !v2 {
	//			fmt.Print("◯")
	//		}else{
	//			fmt.Print("☓")
	//		}
	//	}
	//	fmt.Println()
	//}
	fmt.Println(count)
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <bitset>
#include <cmath>
#include <string>
#define FI first
#define SE second
#define VE vector<int>
#define PB push_back
#define PA pair<int,int>
#define MA make_pair
#define LL long long
#define FOR(i,a,b) for(int i=a;i<b;i++)
#define ROF(i,a,b) for(int i=b-1;i>=a;i--)
#define YES(i) cout<<(i?"YES":"NO")<<endl
#define Yes(i) cout<<(i?"Yes":"No")<<endl
using namespace std;
//
const int INF=1e9+7;
//
int H,N,X,Y;
int SIP[10000][4];
int DP[10000][1<<4];
int main(){
  cin>>H>>N;
  FOR(i,0,N){
    cin>>X>>Y;
    SIP[Y][X]=1;
  }
  FOR(i,0,H){
    FOR(j,0,(1<<4)){
      DP[i][j]=-INF;
    }
  }
  DP[0][0]=0;
  int ans=0;
  FOR(i,0,H){
    FOR(j,0,(1<<4)){
      ans=max(ans,DP[i][j]);
      if(i==H-1){
        continue;
      }
      int tool[2][4];
      FOR(k,0,4){
        tool[0][k]=SIP[i][j];
        tool[1][k]=SIP[i+1][j];
        tool[0][k]|=(j>>k&1);
      }
      DP[i+1][0]=max(DP[i+1][0],DP[i][j]);
      if(!tool[0][0]&&!tool[0][1]&&!tool[1][0]&&!tool[1][1]){
        DP[i+1][3]=max(DP[i+1][3],DP[i][j]+1);
      }
      if(!tool[0][1]&&!tool[0][2]&&!tool[1][1]&&!tool[1][2]){
        DP[i+1][6]=max(DP[i+1][6],DP[i][j]+1);
      }
      if(!tool[0][2]&&!tool[0][3]&&!tool[1][2]&&!tool[1][3]){
        DP[i+1][12]=max(DP[i+1][12],DP[i][j]+1);
      }
      if(!tool[0][0]&&!tool[0][1]&&!tool[1][0]&&!tool[1][1]){
        if(!tool[0][2]&&!tool[0][3]&&!tool[1][2]&&!tool[1][3]){
          DP[i+1][15]=max(DP[i+1][15],DP[i][j]+2);
        }
      }
    }
  }
  cout<<ans<<endl;
  return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <string>
#include <stack>
#include <cmath>
#define ll long long
#define FOR(i,a,b) for(int i=a;i<b;i++)
#define ROF(i,a,b) for(int i=b-1;i>=a;i--)
using namespace std;
//
const int inf=1e9+7;
const int mod=1e9+7;
//
struct poi{
	int X;int Y;int Z;
	bool operator<(const poi&R)const{
		return X==R.X ? Y==R.Y ? Z<R.Z : Y<R.Y : X<R.X;
	}
};
//
ll GCD(ll a,ll b){
	return (b==0)?(a):(GCD(b,a%b));
}
ll LCM(ll a,ll b){
	return a/GCD(a,b)*b;
}
//
int H,N;
int ok[20000][4];
int DP[20000][5];
int main(){
	cin>>H>>N;
	FOR(i,0,H){
		FOR(j,0,4){
			ok[i][j]=1;
		}
	}
	FOR(i,0,N){
		int X,Y;
		cin>>X>>Y;
		ok[Y][X]=0;
	}
	/*
	cout<<endl;
	FOR(i,0,H){
		FOR(j,0,4){
			cout<<ok[i][j]<<" ";
		}
		cout<<endl;
	}
	cout<<endl;
	*/
	//
	if(ok[0][0]&&ok[0][1]&&ok[1][0]&&ok[1][1]){
		DP[0][1]=1;
	}
	if(ok[0][1]&&ok[0][2]&&ok[1][1]&&ok[1][2]){
		DP[0][2]=1;
	}
	if(ok[0][2]&&ok[0][3]&&ok[1][2]&&ok[1][3]){
		DP[0][3]=1;
	}
	if(ok[0][0]&&ok[0][1]&&ok[1][0]&&ok[1][1]&&ok[0][2]&&ok[0][3]&&ok[1][2]&&ok[1][3]){
		DP[0][4]=2;
	}
	//
	if(ok[1][0]&&ok[1][1]&&ok[2][0]&&ok[2][1]){
		DP[1][1]=DP[0][3]+1;
	}
	if(ok[1][1]&&ok[1][2]&&ok[2][1]&&ok[2][2]){
		DP[1][2]=1;
	}
	if(ok[1][2]&&ok[1][3]&&ok[2][2]&&ok[2][3]){
		DP[1][3]=DP[0][1]+1;
	}
	if(ok[1][0]&&ok[1][1]&&ok[2][0]&&ok[2][1]&&ok[1][2]&&ok[1][3]&&ok[2][2]&&ok[2][3]){
		DP[1][4]=2;
	}
	//
	FOR(i,2,H-1){
		DP[i][0]=max({DP[i-2][0],DP[i-2][1],DP[i-2][2],DP[i-2][3],DP[i-2][4],DP[i-1][0],DP[i-1][1],DP[i-1][2],DP[i-1][3],DP[i-1][4]});
		DP[i][1]=max({DP[i-2][0],DP[i-2][1],DP[i-2][2],DP[i-2][3],DP[i-2][4],DP[i-1][3],DP[i-1][0]});
		DP[i][2]=max({DP[i-2][0],DP[i-2][1],DP[i-2][2],DP[i-2][3],DP[i-2][4],DP[i-1][0]});
		DP[i][3]=max({DP[i-2][0],DP[i-2][1],DP[i-2][2],DP[i-2][3],DP[i-2][4],DP[i-1][1],DP[i-1][0]});
		DP[i][4]=max({DP[i-2][0],DP[i-2][1],DP[i-2][2],DP[i-2][3],DP[i-2][4],DP[i-1][0]});
		if(ok[i][0]&&ok[i][1]&&ok[i+1][0]&&ok[i+1][1]){
			DP[i][1]++;
		}else{
			DP[i][1]=max({DP[i][1],DP[i][0]});
		}
		if(ok[i][1]&&ok[i][2]&&ok[i+1][1]&&ok[i+1][2]){
			DP[i][2]++;
		}else{
			DP[i][2]=max({DP[i][2],DP[i][0]});
		}
		if(ok[i][2]&&ok[i][3]&&ok[i+1][2]&&ok[i+1][3]){
			DP[i][3]++;
		}else{
			DP[i][3]=max({DP[i][3],DP[i][0]});
		}
		if(ok[i][0]&&ok[i][1]&&ok[i+1][0]&&ok[i+1][1]&&ok[i][2]&&ok[i][3]&&ok[i+1][2]&&ok[i+1][3]){
			DP[i][4]+=2;
		}else{
			DP[i][4]=max({DP[i][4],DP[i][0]});
		}
	}
	int ans=0;
	/*
	FOR(i,0,H){
		FOR(j,0,5){
			cout<<DP[i][j]<<" ";
		}
		cout<<endl;
	}
	cout<<endl;
	*/
	FOR(i,0,5){
		ans=max(ans,DP[H-2][i]);
	}
	cout<<ans<<endl;
	return 0;
}