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

// #undef DEBUG
// #define DEBUG
/// {{{ DEBUG --- ///
#ifdef DEBUG
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) { o << "{"; for(size_t i = 0; i < v.size(); i++) o << v[i] << (i + 1 != v.size() ? ", " : ""); o << "}"; return o; }
#ifdef USE_COUT
#define dump(...) [&](){auto __debug_tap=make_tuple(__VA_ARGS__);cout<<"["<<__LINE__<< "] "<<#__VA_ARGS__<<" = "<<__debug_tap<<"\n";}()
#else
#define dump(...) [&](){auto __debug_tap=make_tuple(__VA_ARGS__);cerr<<"["<<__LINE__<< "] "<<#__VA_ARGS__<<" = "<<__debug_tap<<"\n";}()
#endif
template<class T> inline void dump2D(T &d, size_t sizey, size_t sizex) { ostream&o=
#ifdef USE_COUT
  cout;
#else
  cerr;
#endif
  for(size_t i = 0; i < sizey; i++) { for(size_t j = 0; j < sizex; j++) o << d[i][j] << " "; o << endl; }
}
#else
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) { for(size_t i = 0; i < v.size(); i++) o << v[i] << (i + 1 != v.size() ? " " : ""); return o; }
#define dump(...) (42)
#define dump2D(...) (42)
#endif
template<int n, class...T> typename enable_if<(n>=sizeof...(T))>::type _ot(ostream &, tuple<T...> const &){}
template<int n, class...T> typename enable_if<(n< sizeof...(T))>::type _ot(ostream & os, tuple<T...> const & t){ os << (n==0?"":", ") << get<n>(t); _ot<n+1>(os, t); }
template<class...T> ostream & operator<<(ostream &o, tuple<T...> const &t){ o << "("; _ot<0>(o, t); o << ")"; return o; }
template<class T, class U> ostream & operator<<(ostream &o, pair<T, U> const &p) { o << "(" << p.first << ", " << p.second << ")"; return o; }
/// }}}--- ///


int f[4][11234];
int h;
int n;

int dp[11234][1 << 3];

int check(int y, int x) {
  for(int i = y; i <= y + 1; i++) for(int j = x; j <= x + 1; j++) {
    if(f[j][i]) return 0;
  }
  return 1;
}

int main() {
  std::ios::sync_with_stdio(false), std::cin.tie(0);
  cin >> h;
  cin >> n;
  for(int i = 0; i < n; i++) {
    int x, y;
    cin >> x >> y;
    f[x][y] = 1;
  }
  
  int ans = 0;
  {
    int y = 0;
    for(int i = 0; i < (1 << 3); i++) {
      int cnt = 0, no = 0;
      for(int ii = 0; ii < 3; ii++) if(i & (1 << ii)) {
        if(!check(y, ii)) no = 1;
        cnt++;
      }
      if(__builtin_popcount(i) >= 2) if(i != 5) no = 1; 
      if(no) continue;
      dp[y][i] = cnt;
      dump(y, i, cnt);
      ans = max(ans, dp[y][j]);
    }
  }

  for(int y = 0; y < h - 2; y++) {
    // yでの置き方
    for(int i = 0; i < (1 << 3); i++) {
      int no = 0;
      for(int ii = 0; ii < 3; ii++) if(i & (1 << ii)) {
        if(!check(y, ii)) no = 1;
      }
      if(__builtin_popcount(i) >= 2) if(i != 5) no = 1; 
      if(no) continue;
      // y + 1での置き方
      for(int j = 0; j < (1 << 3); j++) {
        int cnt = 0, no = 0;
        for(int ii = 0; ii < 3; ii++) if(j & (1 << ii)) {
          if(!check(y + 1, ii)) no = 1;
          cnt++;
        }
        if(__builtin_popcount(j) >= 2) if(j != 5) no = 1; 
        for(int ii = 0; ii < 3; ii++) for(int jj = 0; jj < 3; jj++) 
          if(i&(1 << ii)) if(j &(1<<jj)) {
            if(abs(ii - jj) <= 1) no = 1;
          }
        if(no) continue;
        dp[y+1][j] = max(dp[y+1][j], dp[y][i] + cnt);
        ans = max(ans, dp[y + 1][j]);
      }
    }
  }
  cout << ans << endl;
  return 0;
}

C++: #include <iostream>
#define INF 1e+9
using namespace std;

int b(int a1,int a2,int a3,int a4){
	return a1 + a2 * 2 + a3 * 4 + a4 * 8;
}

int main(){
	int h,n,dp[10010][16] = {};
	int ng[10010][4] = {};
	cin >> h >> n;
	for(int i = 0;i < n;i++){
		int x,y;
		cin >> x >> y;
		ng[y][x] = 1;
	}
	int tmp = 0;
	for(int i = 0;i < 4;i++){
		if(ng[0][i]) tmp += (1 << i);
	}
	for(int i = 0;i < h;i++){
		for(int j = 0;j < 16;j++) dp[i][j] = -INF;
	}
	dp[0][tmp] = 0;
	for(int i = 1;i < h;i++){
		for(int j = 0;j < 16;j++){
			bool a[4] = {};
			for(int k = 0;k < 4;k++){
				if(!((j >> k) & 1) && !ng[i][k]) a[k] = true;
			}
			dp[i][b(ng[i][0],ng[i][1],ng[i][2],ng[i][3])] = max(dp[i][b(ng[i][0],ng[i][1],ng[i][2],ng[i][3])],dp[i - 1][j]);
			if(a[0] && a[1]) dp[i][b(1,1,ng[i][2],ng[i][3])] = max(dp[i][b(1,1,ng[i][2],ng[i][3])],dp[i - 1][j] + 1);
			if(a[1] && a[2]) dp[i][b(ng[i][0],1,1,ng[i][3])] = max(dp[i][b(ng[i][0],1,1,ng[i][3])],dp[i - 1][j] + 1);
			if(a[2] && a[3]) dp[i][b(ng[i][0],ng[i][1],1,1)] = max(dp[i][b(ng[i][0],ng[i][1],1,1)],dp[i - 1][j] + 1);
			if(a[0] && a[1] && a[2] && a[3]) dp[i][15] = max(dp[i][15],dp[i - 1][j] + 2);
		}
	}
	int ma = 0;
	for(int i = 0;i < 16;i++) ma = max(ma,dp[h - 1][i]);
	cout << ma << endl;
	return 0;
}

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

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

#define pb push_back
#define rep(i, n) for(int i = 0; i < (n); i++)
#define dep(i, a, n) for(int i = a; i >= (n); i--)
#define FOR(i, a, n) for(int i = a; i < (n); i++)
#define mod (ll)(1e9+7)
#define int ll
#define INF 100000000

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

signed main() {
	ll h, n, cnt = 0;
  bool s[4][10001];
  cin >> h >> n;
  ll x, y;
  rep(i, n) {
    cin >> x >> y;
    s[x][n - y + 1] = true;
  }
  rep(i, h - 1) {
    if(!s[0][i] && !s[1][i] && !s[0][i + 1] && !s[1][i + 1]) {
      s[0][i] = s[1][i] = s[0][i + 1] = s[1][i + 1] = true;
      cnt++;
    }
    if(!s[2][i] && !s[3][i] && !s[2][i + 1] && !s[3][i + 1]) {
      s[2][i] = s[3][i] = s[2][i + 1] = s[3][i + 1] = true;
      cnt++;
    }
    if(!s[1][i] && !s[2][i] && !s[1][i + 1] && !s[2][i + 1]) {
      s[1][i] = s[2][i] = s[1][i + 1] = s[2][i + 1] = true;
      cnt++;
    }
  }
  /*
  rep(i, h) {
    rep(j, 4) {
      if(s[j][i]) {
        cout << '#';
      } else cout << '.';
    }
    cout << endl;
  }
  */
  cout << cnt << endl;
	return 0;
}

C++: #include <bits/stdc++.h>
#define put(n) cout<<(n)<<endl
#define FOR(i,num,N) for(int(i)=(num);(i)<(N);++(i))
#define RFOR(i,num,N) for(int (i)=(num);(i)>(N);--(i))
#define all(v) (v).begin() , (v).end()
#define rall(v) (v).rbegin() , (v).rend()
using namespace std;

int main(){
    int H,N,F[10100];
    cin>>H>>N;
    long long dp[10100][1<<4],ans;

    FOR(i,0,N){
        int x,y; cin>>x>>y;
        F[y] |= (1<<x);
    }

    FOR(i,0,10100){
        FOR(j,0,(1<<4)){
            dp[i][j] = -1e9;
        }
    }

    dp[0][F[0]] = 0;

    FOR(i,0,H-1){
        FOR(state,0,(1<<4)){
            FOR(bit,0,(1<<3)){
                int next = F[i+1],cnt=0,ok=1;
                FOR(j,0,3){
                    if(!(bit&(1<<j))) continue;
                    if(state&(3<<j)) ok = 0;
                    if(next&(3<<j)) ok = 0;
                    next |= (3<<j);
                    ++cnt;
                }
                if(!ok) continue;
                dp[i+1][next] = max(dp[i+1][next],dp[i][state]+cnt);
            }
        }
    }
    FOR(i,0,(1<<4)) ans = max(ans,dp[H-1][i]);
    put(ans);
}