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>
using namespace std;
 
int C[102][102];
 
void meiro(int W,int H,int c){
  if(C[W][H]!=c){
    return;
  }
 
  C[W][H] = -1;
 
  meiro(W-1,H  ,c);
  meiro(W  ,H+1,c);
  meiro(W+1,H  ,c);
  meiro(W  ,H-1,c);
}
 
int main(){
  while(1){
    int w,h;
    cin >> w >> h;
    if(w==0 && h==0){
      break;
    }
 
    for(int i=0;i<102;i++){
      for(int j=0;j<102;j++){
        C[i][j] = 1919810;
      }
    }
 
    int xs,ys,xg,yg;
    cin >> xs >> ys >> xg >> yg;
 
    int n;
    cin >> n;
 
    int c,d,x,y;
    for(int i=0;i<n;i++){
      cin >> c >> d >> x >> y;
 
      if(d==0){
        for(int j=x;j<x+4;j++){
          for(int k=y;k<y+2;k++){
            C[j][k]=c;
          }
        }
      }else{
        for(int j=x;j<x+2;j++){
          for(int k=y;k<y+4;k++){
            C[j][k]=c;
          }
        }
      }
    }
 
    meiro(xs,ys,C[xs][ys]);
 
    if(C[xg][yg] == -1){
      cout << "OK" << endl;
    }else{
      cout << "NG" << endl;
    }
  }
 
  return 0;
}

C++: #include <queue>
#include <cstring>
#include <iostream>
using namespace std;
int W, H, sx, sy, gx, gy, N, c, d, x, y, r[111][111], vis[111][111];
int dx[4] = { 1, 0, -1, 0 }, dy[4] = { 0, 1, 0, -1 };
int main() {
	while(cin >> W >> H, W | H) {
		cin >> sx >> sy >> gx >> gy; sx--, sy--, gx--, gy--;
		memset(r, 0, sizeof(r));
		cin >> N;
		for(int i = 0; i < N; i++) {
			cin >> c >> d >> x >> y; x--, y--;
			int zx = (d ? 2 : 4), zy = (d ? 4 : 2);
			for(int j = 0; j < zy; j++) {
				for(int k = 0; k < zx; k++) {
					r[y + j][x + k] = c;
				}
			}
		}
		memset(vis, 0, sizeof(vis)); vis[sy][sx] = 1;
		queue<pair<int, int> > que; que.push(make_pair(sx, sy));
		while(!que.empty()) {
			pair<int, int> v = que.front(); que.pop();
			for(int i = 0; i < 4; i++) {
				int tx = v.first + dx[i], ty = v.second + dy[i];
				if(0 <= tx && tx < W && 0 <= ty && ty < H && !vis[ty][tx] && r[ty][tx] == r[v.second][v.first]) {
					vis[ty][tx] = 1;
					que.push(make_pair(ty, tx));
				}
			}
		}
		cout << (vis[gy][gx] ? "OK" : "NG") << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef LL ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<ut,pr> ppr;
typedef priority_queue<pr,Vpr, greater<pr> > PQ;
const int SIZE=5+3*1e+4;
const ut INF=1<<30;
const ld eps=1e-6;
const LL p=7+1e+9;

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

int W, H;
int xs, ys, xg, yg;
int N, C;
int maze[128][128];
bool check[128][128];

int dfs(int x, int y){
	if(x == xg && y == yg)
		return 1;
	
	int res = 0;
	REP(i,4){
		int nx = x + dx[i];
		int ny = y + dy[i];
		if(nx > 0 && nx <= W && ny > 0 && ny <= H && !check[ny][nx] && maze[ny][nx] == C){
			check[ny][nx] = true;
			res |= dfs(nx, ny);
		}
	}
	return res;
}

int main(){
	while(cin >> W >> H && (W || H)){
		memset(maze, 0, sizeof(maze));
		memset(check, 0, sizeof(check));
		cin >> xs >> ys >> xg >> yg >> N;
		int c, d, x, y;
		REP(i,N){
			cin >> c >> d >> x >> y;
			if(d == 0){
				REP(j,2)
					REP(k,4)
						maze[y + j][x + k] = c;
			}
			else{
				REP(j,4)
					REP(k,2)
						maze[y + j][x + k] = c;
			}
		}
		C = maze[yg][xg];
		if(C == 0){
			cout << "NG" << endl;
			continue;
		}
		check[ys][xs] = true;
		int ans = dfs(xs, ys);
		if(ans){
			cout << "OK" << endl;
		}
		else{
			cout << "NG" << endl;
		}
	}
}

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


#define rep(i,n) for(short i = 0; i < n; i++)
#define MAX 50

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

typedef pair<short,short> P;
P S,G;
short w,h;

short color;
	queue<P> que;
	
bool check(short maze[MAX][MAX])
{
	que.push(S);

	color = maze[S.second][S.first];

	short nx,ny;
	while(que.size()){
		P p = que.front();	que.pop();

		if(p == G){
			while(que.size())
				que.pop();
			return true;
		}

		rep(i,4){
			nx = p.first + dx[i], ny = p.second + dy[i];
			
			if(nx > -1 && ny > -1 && nx < w && ny < h &&
				maze[ny][nx] == color){
					maze[ny][nx] = -1;
					que.push(P(nx,ny));
			}

		}
	}


	
	return false;
}

int main(void)
{
	short n,c,d,x,y;
	short maze[MAX][MAX];
	while(cin >> w >> h, w){
	/*	rep(i,MAX){
			rep(j,MAX)
				maze[i][j] = -10;
		}*/
		cin >> S.first >> S.second;
		cin >> G.first >> G.second;
		S.first = S.first / 2;
		S.second= S.second/ 2;

		cin >> n;

		rep(i,n){
			cin >> c >> d >> x >> y;
			x /= 2;
			y /= 2;
			x++;
			y++;

			if(d == 0)
				maze[y][x] = maze[y][x+1] = c;
			else
				maze[y][x] = maze[y+1][x] = c;
		}
		
		if(/*maze[S.second][S.first] > 0 && */maze[S.second][S.first] == maze[G.second][G.first] && check(maze))
			cout << "OK\n";
		else
			cout << "NG\n";

	}
	
	return 0;
}