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<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<cctype>
#include<complex>
#include<iostream>
#include<sstream>
#include<algorithm>
#include<functional>
#include<utility>
#include<vector>
#include<string>
#include<stack>
#include<queue>
#include<map>

using namespace std;
const int dx[] = {1,0,-1,0},dy[] = {0,1,0,-1};
#define INF 1e+9
#define EPS 1e-9
#define rep(i,j) for(int i = 0; i < (j); i++)
#define reps(i,j,k) for(int i = j; i < (k); i++)
typedef long long ll;
int stage[1024][1024];
int xg,yg;
int w,h;
bool dfs(int x,int y,int col){
	if(x == xg && y == yg && stage[x][y] == col){
		return true;
	}
	rep(i,4){
		if(stage[x+dx[i]][y+dy[i]] == 0)continue;
		if(x+dx[i] <= 0 || y+dy[i] <= 0 || x+dx[i] > w || y+dy[i] > h)continue; 
		if(col == stage[x+dx[i]][y+dy[i]]){
			return dfs(x + dx[i], y + dy[i], col);
		}
	}
	return false;
}
int main(){
	while(scanf("%d%d",&w,&h),w|h){
		memset(stage,0,sizeof(stage));
		int xs,ys;
		scanf("%d%d",&xs,&ys);
		scanf("%d%d",&xg,&yg);

		int n;
		scanf("%d",&n);

		rep(q,n){
			int c,d,x,y;
			scanf("%d%d%d%d",&c,&d,&x,&y);
			if(d == 0){
				reps(i,x,x+4){
					reps(j,y,y+2){
						stage[j][i] = c;
					}
				}

			}
			else{
				reps(i,x,x+2){
					reps(j,y,y+4){
						stage[j][i] = c;
					}
				}
			}
		}
		(dfs(xs,ys,stage[xs][ys])) ? puts("OK") : puts("NG");
	}
	return 0;
}

C++: #include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <map>
#include <sstream>
#include <queue>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <iterator>
#include <stack>
#include <list>
using namespace std;
#define INF 1000000000
typedef long long int lli;
typedef pair<int,int> P;

int block[101][101];
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
int w,h,xs,ys,xg,yg,n;
string ans;

void dfs(int x,int y,bool f[][101]){
	if(x==xg&&y==yg){
		ans="OK";
		return;
	}
	for(int i=0; i<4; ++i){
		int nx,ny;
		nx=x+dx[i];
		ny=y+dy[i];
		if(1<=nx&&nx<=w&&1<=ny&&ny<=h&&block[ny][nx]==block[ys][xs]&&!f[ny][nx]){
			f[ny][nx]=true;
			dfs(nx,ny,f);
			f[nx][ny]=false;
		}
	}
}

int main(){
	while(cin >> w >> h){
	if(w==0&&h==0) break;
		cin >> xs >> ys >> xg >> yg >> n;
		for(int i=1; i<=h; ++i){
			for(int j=1; j<=w; ++j){
				block[i][j]=0;
			}
		}
		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<2; ++j){
					for(int k=0; k<4; ++k){
						block[y+j][x+k]=c;
					}
				}
			} else if(d==1){
				for(int j=0; j<4; ++j){
					for(int k=0; k<2; ++k){
						block[y+j][x+k]=c;
					}
				}
			}
		}
		bool f[101][101];
		memset(f,0,sizeof(f));
		f[xs][ys]=true;
		ans="NG";
		dfs(xs,ys,f);
		cout << ans << "\n";
	}
}

C++: #include <cstdio>
#include <cstring>
#include <vector>
#include <map>
#include <algorithm>

#define rep(i, j) FOR(i, 0, j)
#define FOR(i, j, k) for(int i = j; i < k; ++i)

using namespace std;

int w, h, xs, ys, xg, yg, n, c, d, x, y, b[101][101];
int dx[] = {0, -1, 0, 1}, dy[] = {-1, 0, 1, 0};

bool dfs(int x, int y){

  int nx, ny;
  b[x][y] = 0;
  if(x == xg && y == yg) return true;
  bool r = 0;
  rep(i, 4){
    nx = x + dx[i]; ny = y + dy[i];
    if(nx > 0 && nx <= h && ny > 0 && ny <= w && b[nx][ny]==c)r=r||dfs(nx, ny);
  }
  return r;
}

int main(){
  while(scanf("%d %d", &w, &h) && w && h){
    memset(b, 0, sizeof(b));
    scanf("%d%d%d%d", &ys, &xs, &yg, &xg);
    scanf("%d", &n);
    rep(i, n){
      scanf("%d%d%d%d", &c, &d, &y, &x);
      rep(j, (d?4:2)) rep(k, (d?2:4)) b[x + j][y + k] = c;
    }
    /*    rep(i, h){
      rep(j, w) printf("%d ", b[i][j]);
      puts("");
      }*/
    c = b[xs][ys];
    //    printf("%d\n", c);
    //    fprintf(stderr, "error\n");
    if(c > 0 && dfs(xs, ys)) puts("OK");
    else puts("NG");
  }
  return 0;
}

C++: #include<bits/stdc++.h>
#define INF 1e9
using namespace std;
typedef pair<int,int> P;

int main(){
	int w,h;
	while(cin>>w>>h,w,h){
		char board[114][514];
		int pass[114][514];
		
		int xs,ys,xg,yg;
		cin>>xs>>ys>>xg>>yg;
		
		for(int i=0;i<=110;i++){
		for(int j=0;j<=110;j++){pass[i][j]=INF;
			board[i][j]='#';
			}}
		int n;
		cin>>n;
		for(int i=0;i<n;i++){
			char a;
			int b,c,d;
			cin>>a>>b>>c>>d;
			
			if(b==0){
				for(int j=0;j<2;j++)
				for(int k=0;k<4;k++)board[d+j][c+k]=a;
				}
			else{
				for(int j=0;j<2;j++)
				for(int k=0;k<4;k++)board[d+k][c+j]=a;
				}	
			}
		
		queue<P>Q;
		Q.push(P(ys,xs));
		pass[ys][xs]=0;
		
		while(Q.size()){
			P p=Q.front();
			Q.pop();
			
			if(p.first==yg&&p.second==xg)break;
			
			int dir[2][4]={{1,0,-1,0},{0,1,0,-1}};
			for(int i=0;i<4;i++){
				int ny=p.first+dir[0][i];
				int nx=p.second+dir[1][i];
				
				if(0<=ny&&ny<=h&&0<=nx&&nx<=w&&board[ny][nx]==board[ys][xs]&&pass[ny][nx]==INF){
					Q.push(P(ny,nx));
					pass[ny][nx]=pass[p.first][p.second]+1;
					}
				}
			}
		
		if(pass[yg][xg]!=INF)cout<<"OK"<<endl;
		else cout<<"NG"<<endl;
		
		}
		return 0;
	}