Go: package main

import (
	"bufio"
	"os"
	"strings"
	"strconv"
	"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

var (
	dx = []int{0, -1, 0, 1}
	dy = []int{1, 0, -1, 0}
)

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		w, _ := strconv.Atoi(buf[0])
		h, _ := strconv.Atoi(buf[1])
		if w == 0 && h == 0 {
			break
		}
		scanner.Scan()
		buf_ := strings.Split(scanner.Text(), " ")
		xs, _ := strconv.Atoi(buf_[0])
		ys, _ := strconv.Atoi(buf_[1])
		scanner.Scan()
		buf__ := strings.Split(scanner.Text(), " ")
		xg, _ := strconv.Atoi(buf__[0])
		yg, _ := strconv.Atoi(buf__[1])
		xs--
		ys--
		xg--
		yg--
		scanner.Scan()
		n, _ := strconv.Atoi(scanner.Text())
		field := make([][]int, 100)
		for i := range  field {
			field[i] = make([]int, 100)
		}
		visited := make([][]bool, 100)
		for i := range visited {
			visited[i] = make([]bool, 100)
		}
		for i := 0; i < n; i++ {
			scanner.Scan()
			buf___ := strings.Split(scanner.Text(), " ")
			c, _ := strconv.Atoi(buf___[0])
			d, _ := strconv.Atoi(buf___[1])
			x, _ := strconv.Atoi(buf___[2])
			y, _ := strconv.Atoi(buf___[3])
			x--
			y--
			switch d {
			case 0:
				for j := 0; j < 4; j++ {
					for k := 0; k < 2; k++ {
						field[x+j][y+k] = c
					}
				}
			case 1:
				for j := 0; j < 2; j++ {
					for k := 0; k < 4; k++ {
						field[x+j][y+k] = c
					}
				}
			}
		}
		if field[xs][ys] != field[xg][yg] || // スタートとゴールの色が等しくないと"NG"
			field[xs][ys] == 0 { // スタートの色が無職
			fmt.Println("NG")
			continue
		}
		Q := make([]Entry, 0)
		visited[xs][ys] = true
		Q = append(Q, Entry{xs, ys})
		for len(Q) > 0 {
			row := Q[0].x
			col := Q[0].y
			Q = Q[1:]
			for i := 0; i < 4; i++ {
				if 0 <= row+dx[i] && row+dx[i] < w &&
					0 <= col+dy[i] && col+dy[i] < h && // 移動可能な範囲内かどうか
					!visited[row + dx[i]][col + dy[i]] && // 訪問済みか
					field[row+dx[i]][col+dy[i]]==field[row][col] { // 色が同じかどうか
						visited[row+dx[i]][col+dy[i]] = true
						Q = append(Q, Entry{row+dx[i],col+dy[i]})
				}
			}
		}
		if visited[xg][yg] {
			fmt.Println("OK")
		} else {
			fmt.Println("NG")
		}
	}
}

type Entry struct {
	x, y int
}

C++: #include<iostream>
#include<cstring>

using namespace std;

int map[105][105];
int xg,yg;
int w,h;
int dx[]={0,0,-1,1};
int dy[]={-1,1,0,0};

bool check(int x,int y)
{
  if(x==xg && y==yg)
    return true;
  if(map[x][y]==-1)
    return false;
  if(x>h||y>w||x<=0||y<=0)
    return false;
  
  char buf=map[x][y];
  map[x][y]=-1;
  for(int i=0;i<4;i++)
    {
      if(x+dx[i]<=h && x+dx[i]>0 &&
	 y+dy[i]<=w && y+dy[i]>0 &&
	 map[x+dx[i]][y+dy[i]]==buf && 
	 check(x+dx[i],y+dy[i])
	 )
	return true;
    }
  return false;
}
int main()
{
  for(;cin>>w>>h,w;)
    {
      memset(map,-1,sizeof(map));
      int xs,ys;
      cin>>xs>>ys;
      cin>>xg>>yg;
      int n;
      cin>>n;
      for(int i=0;i<n;i++)
	{
	  int c,d,x,y;
	  cin>>c>>d>>y>>x;
	  if(d==0)
	    {
	      for(int xx=x;xx<x+2;xx++)
		for(int yy=y;yy<y+4;yy++)
		  map[xx][yy]=c;
	    }
	  else
	    {
	      for(int xx=x;xx<x+4;xx++)
		for(int yy=y;yy<y+2;yy++)
		  map[xx][yy]=c;
	    }
	}
      if(check(xs,ys))
	cout<<"OK"<<endl;
      else 
	cout<<"NG"<<endl;      
    }
}

C++: #include <bits/stdc++.h>
#include<stdio.h>
using namespace std;
#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(a) begin(a),end(a)
#define MS(m,v) memset(m,v,sizeof(m))
#define D10  fixed<<setprecision(10)
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> P;
typedef long long ll;
const ll INF = 114514810;
const ll MOD = 1000000007;
const double EPS = 1e-8;
const double PI = acos(-1.0);
struct edge
{
	int from, to, cost;
	bool operator < (const edge& e) const { return cost < e.cost; }
	bool operator >(const edge& e) const { return cost > e.cost; }
};
int dx[] = { -1, 0, 0, 1 }; int dy[] = { 0, -1, 1, 0 };
bool valid(int x, int y, int h, int w) { return (x >= 0 && y >= 0 && x < h&&y < w); }
///*************************************************************************************///
///*************************************************************************************///
///*************************************************************************************///


int main()
{
	int w, h;
	while (cin >> w >> h, w)
	{
		vector<vi> v(h, vi(w));
		int sx, sy, gx, gy;
		cin >> sy >> sx >> gy >> gx;
		sx--; sy--; gx--; gy--;
		int n; cin >> n;
		while (n--)
		{
			int c, d, x, y;
			cin >> c >> d >> x >> y;
			x--; y--;
			if (d==0)
			{
				REP(i, 4)REP(j, 2)
				{
					v[x + i][y + j] = c;
				}
			}
			else
			{
				REP(i, 2)REP(j, 4)
				{
					v[x + i][y + j] = c;
				}
			}
		}
		int co = v[sx][sy];
		if (co == 0)
		{
			puts("NG");
			continue;
		}
		queue<P> que;
		que.push(P(sx, sy));
		bool f = false;
		while (que.size())
		{
			P tmp = que.front();
			que.pop();
			int tx = tmp.first, ty = tmp.second;
			if (tx == gx&&ty == gy)
			{
				f = true;
				break;
			}
			v[tx][ty] = 0;
			REP(i, 4)
			{
				int nx = tx + dx[i], ny = ty + dy[i];
				if (valid(nx, ny, h, w) && v[nx][ny] == co) que.push(P(nx, ny));
			}
		}
		puts(f ? "OK" : "NG");
	}
}

C++: #include <iostream>
using namespace std;

int F[105][105];


void DFS(int Y,int X,int c){
  if(F[Y][X] != c){
    return;
  }

  F[Y][X] = -1;
  DFS(Y-1,X  ,c);
  DFS(Y  ,X+1,c);
  DFS(Y+1,X  ,c);
  DFS(Y  ,X-1,c);
}


int main(){
  int w,h,xs,ys,xg,yg,n;
  while(1){
    cin >> w >> h;
    if(w == 0 && h == 0)
      break;

      for(int i=0;i<105;i++){
        for(int j=0;j<105;j++){
                F[i][j]=0;
        }
      }
    cin >> xs >> ys >> xg >> yg >> n;


    for(int i=0;i<n;i++){
      int c,d,x,y;
      cin >> c >> d >> x >> y;
      if(d == 0){
        for(int j=0;j<4;j++){
          F[x+j][y] = c;
          F[x+j][y+1] = c;
        }
      } else {
        for(int j=0;j<4;j++){
          F[x][y+j] = c;
          F[x+1][y+j] = c;
        }
      }
    }

  //DFS(xs,ys,F[xs][ys]);
  if(F[xg][yg] == -1){
    cout << "OK" << endl;
  } else {
    cout << "NG" <<endl;
  }
  }
}

C++: #include<iostream>
#include<cstdio>
#include<queue>
#include<vector>
#include<algorithm>
#define F first
#define S second 
using namespace std;
typedef pair<int,int> P;
int w,h,sx,sy,gx,gy,fc;
int imap[110][110];
const int dx[4] = {0,1,0,-1};
const int dy[4] = {1,0,-1,0};
bool found;
void Init(){
  for(int i=0;i<110;i++){
    for(int j=0;j<110;j++){
      imap[i][j] = -1;
    }
  }
}

void display(){
 for(int i=0;i<h;i++){
      for(int j=0;j<w;j++){
	printf("%3d ",imap[i][j]);
      }
      cout << endl;
    }
}

void draw(int c,int d,int x,int y){
  int limy,limx;
  limy = d==1?4:2;
  limx = d==1?2:4;
  for(int i=0;i<limy && i<h;i++){
    for(int j=0;j<limx && j<w;j++){
      imap[y+i][x+j] = c;
    }
  }
}

void rec(int px,int py){
  if(px == gx && py == gy){
    found = true;
    return;
  }
  for(int i=0;i<4;i++){
    int nx = px+dx[i], ny = py+dy[i];
    if(!found && 0<=nx && nx <w && 0<=ny && ny<h && imap[ny][nx] == fc){
      imap[ny][nx] = -1;
      rec(nx,ny);
    }
  }
}


bool isMaze(){
  rec(sx,sy);
  if(found)return true;
  return false;
}

int main(){
  int n,c,d,x,y;
  while(cin >> w >> h  && w && h){
    found = false;
    cin >> sx >> sy;
    cin >> gx >> gy;
    cin >> n;
    Init();
    for(int i=0;i<n;i++){
      cin >> c >> d >> x >> y;
      draw(c,d,x,y);
    }

    
    fc = imap[sy][sx];
    if(fc == -1)cout << "NG" << endl;
    else{
      if(isMaze())cout << "OK" << endl;
      else cout << "NG" << endl;
    }

  }
  return 0;
}