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 <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];

int dfs(int x, int y){
	if(x == xg && y == yg)
		return 1;
	maze[y][x] = 0;
	REP(i,4){
		int nx = x + dx[i];
		int ny = y + dy[i];
		if(maze[ny][nx] == C){
			if(dfs(nx, ny))
				return 1;
		}
	}
	return 0;
}

int main(){
	while(cin >> W >> H && (W || H)){
		memset(maze, 0, sizeof(maze));
		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 || maze[ys][xs] == 0){
			cout << "NG" << endl;
			continue;
		}
		int ans = dfs(xs, ys);
		if(ans){
			cout << "OK" << endl;
		}
		else{
			cout << "NG" << endl;
		}
	}
}

C++: #include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int fie[101][101],ans,gol[101][101],st[101][101],col,muki,bx,by;
int bex[]={0,1,0,-1},bey[]={1,0,-1,0},cou;
int func(int y,int x){
    if(y<1||x<1)return 0;
    if(fie[y][x]==0)return 0;
    if(fie[y][x]==6){
        cou=1;
        return 0;
    }
    if(cou==1)return 0;
    if(fie[y][x]!=ans){
        fie[y][x]=0;
        return 0;
    }
    if(fie[y][x]==ans){
        for(int i=0;i<4;i++){
            func(y+bey[i],x+bex[i]);
        }
    }
    return 0;
}
int main(){
    int a,b,sx,sy,gx,gy,n;
    for(;;){
        cin>>a>>b;
        if(a==0&&b==0)break;
        fill(fie[0],fie[0]+101*101,0);
        cin>>sx>>sy>>gx>>gy;
        cin>>n;
        for(int i=0;i<n;i++){
            cin>>col>>muki>>bx>>by;
            if(muki==0){
                for(int i=0;i<=1;i++){
                    for(int j=0;j<=3;j++){
                        fie[by+i][bx+j]=col;
                    }
                }
            }
            if(muki==1){
                for(int i=0;i<=3;i++){
                    for(int j=0;j<=1;j++){
                        fie[by+i][bx+j]=col;
                    }
                }
            }
        }
        fie[gy][gx]=6;
        ans=fie[sy][sx];
        func(sy,sx);
        if(cou==1)cout<<"OK"<<endl;
        else cout<<"NG"<<endl;
        cou=0;
    }
return 0;
}

C++: 		if(ban[x][y+1]==c&&visited[x][y+1]==false){
			visited[x][y+1]=true;
			if(dfs(x,y+1,c))return true;
		}
		if(x>=2&&ban[x-1][y]==c&&visited[x-1][y]==false){
			visited[x-1][y]=true;
			if(dfs(x-1,y,c))return true;
		}
		if(y>=2&&ban[x][y-1]==c&&visited[x][y-1]==false){
			visited[x][y-1]=true;
			if(dfs(x,y-1,c))return true;
		}
		return false;
	}


int main(){

	while(cin>>w>>h&&w&&h){
	cin>>xs>>ys>>xg>>yg>>n;
	for(int i=0;i<101;i++)
	for(int j=0;j<101;j++)ban[i][j]=-1,visited[i][j]=false;
	
	for(int i=0;i<n;i++){
		int c,d,x,y;
		cin>>c>>d>>x>>y;
		if(!d){
			for(int i=x;i<x+4;i++){
				for(int j=y;j<y+2;j++){
					ban[i][j]=c;
				}
			}
		}
		else{
		for(int i=x;i<x+2;i++){
				for(int j=y;j<y+4;j++){
					ban[i][j]=c;
				}
			}
		}
		}
		if(dfs(xs,ys,ban[xs][ys]))cout<<"OK"<<endl;
	else cout<<"NG"<<endl;
	}
	return 0;
	}

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

int w, h;
int sx, sy;
int gx, gy;
int t[102][102];

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

bool dfs(int x, int y){
  if(x == gx && y == gy){
    return true;
  }

  char c = t[y][x];
  t[y][x] = 0;

  for(int i = 0; i < 4; i++){
    int nx = x + dx[i];
    int ny = y + dy[i];

    if(nx < 0 || w <= nx || ny < 0 || h <= ny) continue;
    if(t[ny][nx] != c) continue;
    if(dfs(nx, ny)) return true;
  }

  return false;
}

void solve(){
  if(t[sy][sx] == 0){
    cout << "NG" << endl;
    return;
  }
  cout << (dfs(sx, sy) ? "OK" : "NG") << endl;
}

int main(){
  while(cin >> w >> h, w || h){
    cin >> sx >> sy; sx--; sy--;
    cin >> gx >> gy; gx--; gy--;

    int n;
    cin >> n;

    memset(t, 0, sizeof(t));

    for(int i = 0; i < n; i++){
      int c, d, x, y;
      cin >> c >> d >> x >> y;
      x--;
      y--;

      if(d == 0){ //脱即捉
        for(int i = y; i < y + 2; i++){
          for(int j = x; j < x + 4; j++){
            t[i][j] = c;
          }
        }
      }
      else{ //巽存側
        for(int i = y; i < y + 4; i++){
          for(int j = x; j < x + 2; j++){
            t[i][j] = c;
          }
        }
      }
    }

    solve();
  }
}