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[ys][xs];
		if(C == 0){
			cout << "NG" << endl;
			continue;
		}
		if(dfs(xs, ys)){
			cout << "OK" << endl;
		}
		else{
			cout << "NG" << endl;
		}
	}
}

C++: #include <iostream>
using namespace std;
  
int F[102][102];
  
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<20; i++){
      for(int j=0; j<20; j++){
        F[i][j]=-1;
      }
    }
      
    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;
        }
      }
    }

  if(F[xs][ys] == 0){
    cout << "NG" << endl;
  } else {
    DFS(xs,ys,F[xs][ys]);
  
    if(F[xg][yg] == -1){
      cout << "OK" << endl;
    } else {
      cout << "NG" <<endl;
    }
  }

}
}

C++: #include <cstdio>
#include <cctype>
#include <utility>
#include <vector>
#include <queue>
#include <functional>
using namespace std;

#define gcu getchar_unlocked
#define pcu putchar_unlocked
#define _T template <typename T>
#define _HT template <typename H, typename... T>
#define _il inline
#define _in _il int in
#define _sc _il bool scan
_T T in(int c){T n=0;bool m=false;while(isspace(c)){c=gcu();}if(c=='-')m=true,c=gcu();
	do{n=10*n+(c-'0'),c=gcu();}while(c>='0'&&c<='9');return m?-n:n;}
_in() {return in<int>(gcu());}
_T T scan(T &n){int c=gcu();return c==EOF?false:(n=in<T>(c),true);}
_sc(char &c){c=gcu();gcu();return c!=EOF;}
#ifdef _GLIBCXX_STRING
_sc(string &s){int c;s="";
	for(;;){c=gcu();if(c=='\n'||c==' ')return true;else if(c==EOF)return false;s+=c;}}
#endif
_HT _sc(H &h, T&&... t){return scan(h)&&scan(t...);}
#define _vo _il void out
#define _vl _il void outl
_vo(bool b) {pcu('0'+b);}
_vo(const char *s){while(*s)pcu(*s++);}
_vo(char c){pcu(c);}
#ifdef _GLIBCXX_STRING
_vo(string s){for(char c:s)pcu(c);}
#endif
_T _vo(T n){static char buf[20];char *p=buf;
	if(n<0)pcu('-'),n*=-1;if(!n)*p++='0';else while(n)*p++=n%10+'0',n/=10;
	while (p!=buf)pcu(*--p);}
_vl(){out('\n');}
#ifdef _GLIBCXX_VECTOR
_T _vo(vector<T> &v){for(T &x:v)out(&x == &v[0]?"":" "),out(x);outl();}
#endif
_HT _vo(H&& h, T&&... t){out(h);out(move(t)...);}
template <typename... T> _vl(T&&... t){out(move(t)...);outl();}

using V = vector<int>;
using VV = vector<V>;
struct P {int x, y;};

int main() {
	int dx[] = {4, 2}, dy[] = {2, 4};
	for (int w, h; w = in(), h = in();) {
		P s = {in() - 1, in() - 1}, g = {in() - 1, in() - 1};
		int n = in();
		VV m(h, V(w));
		while (n--) {
			int c = in(), d = in(), x = in() - 1, y = in() - 1;
			for (int i = 0; i < dy[d]; i++)
				for (int j = 0; j < dx[d]; j++)
					m[i + y][j + x] = c;
		}
		int c = m[s.y][s.x];
		m[s.y][s.x] = 0;
		function<bool(int, int)> f = [&](int x, int y) {
			if (x == g.x && y == g.y)
				return true;
			P d = {1, 0};
			for (int i = 0; i < 4; i++) {
				int tx = x + d.x, ty = y + d.y;
				if (tx >= 0 && ty >= 0 && tx < w && ty < h && m[ty][tx] == c) {
					m[ty][tx] = 0;
					if (f(tx, ty))
						return true;
				}
				swap(d.x, d.y *= -1);
			}
			return false;
		};
		outl(c ? f(s.x, s.y) ? "OK" : "NG" : "NG");
	}
}