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 i := 0; i < 3; i++ {
		for j := 0; j < H-1; j++ {


			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 <bits/stdc++.h>
using namespace std;

#define INF 1.1e9
#define LINF 1.1e18
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define RREP(i, n) for (int i = (n) - 1; i >= 0; i--)
#define ALL(v) (v).begin(), (v).end()
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define BIT(x, n) bitset<n>(x)
#define PI 3.14159265358979323846

typedef long long ll;
typedef pair< int, int > P;   
typedef pair< int, P > PP;

//-----------------------------------------------------------------------------

int h, n;
bool used[4][10000];

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    cin >> h >> n;
    REP(i, n) {
        int x, y;
        cin >> x >> y;
        used[x][y] = true;
    }
    int ans = 0;
    REP(i, h - 1) {
        REP(j, 3) {
            if (used[j][i] || used[j + 1][i] || used[j][i + 1] || used[j + 1][i + 1]) continue;
            used[j][i] = used[j + 1][i] = used[j][i  +1] = used[j + 1][i + 1] = true;
            ans++;
        }
    }
    cout << ans << endl;

    return 0;
}

C++: // #pragma GCC target ("arch=ivybridge")
#pragma GCC optimize ("O3")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep2(i, m, n) for (int i = (m); i < (n); i++)
#define repr(i, n) for (int i = (n)-1; i >= 0; i--)
#define repr2(i, m, n) for (int i = (n)-1; i >= (m); i--)
#define all(x) x.beign(), x.end()

#define MaxH 10005
int dp[MaxH][5];
int no[MaxH];
int h, n;

signed main() {
  cin.tie(0); ios_base::sync_with_stdio(0);

  cin >> h >> n;
  rep(_, n) {
    int x, y; cin >> x >> y;
    no[y] |= 1 << x;
  }

  int on[] = {0, 3, 6, 12, 15};
  int v[] = {0, 1, 1, 1, 2};
  rep(r, h-1) {
    rep(i, 5) {
      int ng = on[i] | no[r];
      rep(j, 5)
        if ((ng & on[j]) == 0 && (no[r+1] & on[j]) == 0)
          dp[r+1][j] = max(dp[r+1][j], dp[r][i] + v[j]);
    }
  }

  cout << *max_element(dp[h-1], dp[h]) << "\n";
}

C++: #include "bits/stdc++.h"
using namespace std;
typedef long long ll;
#define _overload4(_1,_2,_3,_4,name,...) name
#define _overload3(_1,_2,_3,name,...) name
#define _overload2(_1,_2,name,...) name
#define _re(n) _rep(i,n)
#define _rep(i,n) _repi(i,0,n)
#define _repi(i,a,b) for(ll i=a;i<b;++i)
#define _repc(i,a,b,c) for(ll i=a;i<b;i+=c)
#define rep(...) _overload4(__VA_ARGS__,_repc,_repi,_rep,_re)(__VA_ARGS__)
#define _rre(n) _rrep(i,n)
#define _rrep(i,n) _rrepi(i,0,n)
#define _rrepi(i,a,b) for(ll i=b-1;i>=a;i--)
#define _rrepc(i,a,b,c) for(ll i=a+(b-a-1)/c*c;i>=a;i-=c)
#define rrep(...) _overload4(__VA_ARGS__,_rrepc,_rrepi,_rrep,_rre)(__VA_ARGS__)
#define sum(...) accumulate(range(__VA_ARGS__),0)
#define _range(i) (i).begin(),(i).end()
#define _rangek(i,k) (i).begin(),(i).begin()+k
#define range(...) _overload2(__VA_ARGS__,_rangek,_range)(__VA_ARGS__)
#define LINF (ll)1000000000000000000
#define MOD (ll)1000000007
#define INF (int)1000000007
#define Yes(i) out(i?"Yes":"No")
#define YES(i) out(i?"YES":"NO")
#define INT(...) int __VA_ARGS__;in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;in(__VA_ARGS__)
#define STR(...) string __VA_ARGS__;in(__VA_ARGS__)
#define CHR(...) char __VA_ARGS__;in(__VA_ARGS__)
#define DBL(...) double __VA_ARGS__;in(__VA_ARGS__)
#define vec(type,name,size) vector<type> name(size);
#define VEC(type,name,size) vector<type> name(size);in(name)
struct aaa{aaa(){cin.tie(0); cout.tie(0); ios::sync_with_stdio(0); cout<<fixed<<setprecision(15);};}aaaaaaa;
inline void in() {}
template<typename T>
istream& operator >> (istream& is, vector<T>& vec);
template<typename T,typename L>
istream& operator >> (istream& is, pair<T,L>& p);
template<typename T>
ostream& operator << (ostream& os, vector<T>& vec);
template<typename T,typename L>
ostream& operator << (ostream& os, pair<T,L>& p);
template<typename T>
istream& operator >> (istream& is, vector<T>& vec){for(T& x: vec) is >> x;return is;}
template<typename T,typename L>
istream& operator >> (istream& is, pair<T,L>& p){is >> p.first;is >> p.second;return is;}
template<typename T>
ostream& operator << (ostream& os, vector<T>& vec){os << vec[0];rep(i,1,vec.size()){os << ' ' << vec[i];}return os;}
template<typename T,typename L>
ostream& operator << (ostream& os, pair<T,L>& p){os << p.first << " " << p.second;return os;}
template <class Head, class... Tail>
inline void in(Head&& head,Tail&&... tail){cin>>head;in(move(tail)...);}
template <class T>
inline void out(T t){cout<<t<<'\n';}
inline void out(){cout<<'\n';}
template <class Head, class... Tail>
inline void out(Head head,Tail... tail){cout<<head<<' ';out(move(tail)...);}


int main(){
    INT(h,n);
    vector<array<int,4>>block(h+1);
    rep(n){
        INT(x,y);
        block[y][x]=1;
    }
    fill(block[h].begin(), block[h].end(), 1);
    int ans=0;
    rep(i,1,h){
        if(!(block[i-1][0]+block[i][0]+block[i-1][1]+block[i][1])){
            block[i-1][0]=block[i][0]=block[i-1][1]=block[i][1]=1;
            ans++;
        }
        if(!(block[i-1][2]+block[i][2]+block[i-1][3]+block[i][3])){
            block[i-1][2]=block[i][2]=block[i-1][3]=block[i][3]=1;
            ans++;
        }
        if(!(block[i-1][2]+block[i][2]+block[i-1][1]+block[i][1])&&(block[i][0]+block[i][3]+block[i+1][0]+block[i+1][1]+block[i+1][2]+block[i+1][3])){
            block[i-1][2]=block[i][2]=block[i-1][1]=block[i][1]=1;
            ans++;
        }
    }
    out(ans);
}

C++: #include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;

#define pb push_back
#define rep(i, a, n) for(int i = (a); i < (n); i++)
#define dep(i, a, n) for(int i = (a); i >= (n); i--)
#define mod (ll)(1e9+7)
#define int ll

__attribute__((constructor))
void initial() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}

signed main() {
  int h, n;
  cin >> h >> n;

  bool t[4][10005] = {};

  rep(i, 0, n) {
    int x, y;
    cin >> x >> y;
    t[x][y] = true;
  }
  int ans = 0;
  rep(i, 0, h - 1) {
    if(!t[0][i] && !t[1][i] && !t[0][i + 1] && !t[1][i + 1]) {
      ans++, t[1][i] = true, t[0][i + 1] = true, t[1][i + 1] = true;
    }
    if(!t[2][i] && !t[3][i] && !t[2][i + 1] && !t[3][i + 1]) {
      ans++, t[2][i] = true, t[2][i + 1] = true, t[3][i + 1] = true;
    }
    if(!t[1][i] && !t[2][i] && !t[1][i + 1] && !t[2][i + 1]) {
      int k = 0;
      while(!t[0][i] && !t[1][i] && !t[2][i] && !t[3][i] && i < h) k++;
      if(k < 2 || k % 2) {
        ans++, t[1][i + 1] = true, t[2][i + 1] = true;
      }
    }
  }
  cout << ans << endl;
}