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 <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>
#include <fstream>

using namespace std;

#define FOR(i,a,b) for(long long i=(a);i<(b);i++)
#define REP(i,N) for(long long i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define fi first
#define se second

#define PI acos(-1.0)
#define INF 1000000007
#define MOD 1000000007
#define EPS 1e-10
#define MAX_N 100100
#define MAX_M 100100

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<double, double> PD;
typedef pair<string, ll> PS;
typedef vector<ll> V;
typedef pair<P, char> PC;
typedef pair<int, string> PSI;

int w, h, sx, sy, gx, gy;
int n, c, d, x, y;

bool ans;

int table[110][110];
int dis[110][110];

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

void solve(){
	REP(i, 110)REP(j, 110)dis[i][j] = INF;
	dis[sy][sx] = 0;

	queue<P> que;
	que.push(P(sy, sx));

	while (que.size()){
		P p = que.front(); que.pop();
		int cx = p.second, cy = p.first;

		if (y == gy&&x == gx)break;

		REP(i, 4){
			int nx = cx + dx[i], ny = cy + dy[i];
			if (nx >= 0 && nx < w&&ny >= 0 && ny < h){
				if (table[ny][nx] == table[cy][cx]
					&&dis[ny][nx] == INF){
					dis[ny][nx] = dis[cy][cx] + 1;
					que.push(P(ny, nx));
				}
			}
		}
	}
}

int main(){
	while (cin >> w >> h&&w + h){
		ans = 0;
		REP(i, 110)REP(j, 110){
			table[i][j] = 0;
		}
		cin >> sx >> sy >> gx >> gy;
		dis[sy][sx] = 1;

		cin >> n;
		REP(i, n){
			cin >> c >> d >> x >> y;
			if (d == 0){
				REP(i, 2){
					REP(j, 4){
						table[y + i][x + j] = c;
					}
				}
			}
			else{
				REP(i, 4){
					REP(j, 2){
						table[y + i][x + j] = c;
					}
				}
			}
		}
		//REP(i, h){
		//	REP(j, w){
		//		cout << table[i][j] << " ";
		//	}
		//	cout << endl;
		//}
		//cout << "!" << endl;
		//solve();
		//REP(i, h){
		//	REP(j, w){
		//		cout << dis[i][j] << " ";
		//	}
		//	cout << endl;
		//}
		if (dis[gy][gx] != INF&&table[sy][sx] != 0 && table[gy][gx] != 0)cout << "OK" << endl;
		else cout << "NG" << endl;
	}
}

C++: #include<iostream>
#include<cstring>
#include<queue>
#include<map>
using namespace std;
int C,goal,n,x,y,xs,ys,xg,yg,mas[110][110]={{0}};
int dx[4]={0,0,1,1};
int dy[4]={0,1,0,1};
int d[110][110];
typedef pair<int,int>P;

int bfs();
int main(){

  while(1){
    goal=0;
    memset(mas,0,sizeof(mas));
    cin >> x >> y;//ボードの大きさ。 ※：x=横。y=縦。
    if(x==0 && y==0){
      break;
    }
    cin >> xs >> ys;//スタート地点。
    cin >> xg >> yg;//ゴール地点。
    cin >> n;//ブロックの数。
    
    //色染め。
    int color,dire,xx,yy;
    for(int t=0;t<n;t++){
      cin >> color >> dire >> xx >> yy;

      //横長。
      if(dire==0){
	for(int i=0;i<2;i++){
	  for(int j=0;j<4;j++){
	    mas[yy+i][xx+j]=color;
	  }
	}
      }
      
      //縦長。
      else{
	for(int i=0;i<4;i++){
	  for(int j=0;j<2;j++){
	    mas[yy+i][xx+j]=color;
	  }
	}
      }
      
    }
    
    //通る色　摘出。
    C=mas[ys][xs];
    //cout << "color:" << C << endl;
    
    if(C!=0){

      bfs();

    
      if(goal==1){
	cout << "OK" << endl;
      }
      else{
	cout << "NG" << endl;
      }
    }
    else{
      cout << "NG" << endl;
    }
  }
}

int bfs(){
  queue<P>que;
  memset(d,-1,sizeof(d));
  que.push(P(ys,xs));
  d[ys][xs]=0;
  while(!que.empty()){
    P p=que.front();
    que.pop();
    if(p.first==yg && p.second==xg){
      goal=1;
      break;
    }
    for(int i=0;i<4;i++){
      int ny=p.first+dy[i];
      int nx=p.second+dx[i];
      if(mas[ny][nx]==C && ny>=1 && ny<=y && nx>=1 && nx<=x && d[ny][nx]==-1){
	d[ny][nx] = 1;
	que.push(P(ny,nx));
      }
    }
  }
  return (0);
}

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

#define BLANK 0

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

bool dfs(int color, int x, int y, int gx, int gy, vector<vector<int> >& blocks){
  if(x == gx && y == gy){ return true; }
  blocks[x][y] = BLANK;
  for(int i = 0; i < 4; i++)
    if(blocks[x + dx[i]][y + dy[i]] == color)
      if(dfs(color, x + dx[i], y + dy[i], gx, gy, blocks))
        return true;
  return false;
}


int main(void){
  while(true){
    int w, h;
    cin >> w >> h;
    if(w == 0 && h == 0){ break; }

    int sx, sy, gx, gy;
    cin >> sx >> sy;
    cin >> gx >> gy;

    int n;
    cin >> n;

    vector<vector<int> > blocks(w + 2, vector<int>(h + 2, BLANK));
    for(int i = 0; i < n; i++){
      int c, d, x, y;
      cin >> c >> d >> x >> y;
      int now_w = (d == 0) ? 4 : 2;
      int now_h = (d == 0) ? 2 : 4;
      for(int j = 0; j < now_w; j++)
        for(int k = 0; k < now_h; k++)
          blocks[x + j][y + k] = c;
    }

    // ????????????
    if(blocks[sx][sy] == BLANK){
      cout << "NG" << endl;
      continue;
    }

    // ??????
    if(dfs(blocks[sx][sy], sx, sy, gx, gy, blocks)){ cout << "OK" << endl; }
    else{ cout << "NG" << endl; }
  }

  return 0;
}