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>
int block[100][100];
int visited[100][100];
bool memo[100][100];
int w, h, xs, ys, xg, yg, n;
int d[2][4]={{0,0,-1,1},{-1,1,0,0}};
bool dfs(int x, int y) {
    if (visited[y][x]) return memo[y][x];
    if (x==xg-1&&y==yg-1) return true;
    visited[y][x]=1;
    for (int i=0; i<4; i++) {
        int nx=x+d[0][i], ny=y+d[1][i];
        if (nx>=0&&nx<w&&ny>=0&&ny<h&&block[y][x]==block[ny][nx]) {
            if (dfs(nx,ny)) {
                memo[y][x]=true;
                return true;
            }
        }
    }
    memo[y][x]=false;
    return false;
}
int main() {
    while (scanf("%d%d",&w,&h)) {
        if (!w&&!h) break;
        scanf("%d%d%d%d%d",&xs,&ys,&xg,&yg,&n);
        for (int i=0; i<n; i++) {
            int c, d, x, y;
            scanf("%d%d%d%d",&c,&d,&x,&y);
            if (d) {
                for (int j=y-1; j<y+3; j++) {
                    for (int k=x-1; k<x+1; k++) {
                        block[j][k]=c;
                    }
                }
            } else {
                for (int j=x-1; j<x+3; j++) {
                    for (int k=y-1; k<y+1; k++) {
                        block[k][j]=c;
                    }
                }
            }
        }
        /*for (int i=0; i<h; i++) for (int j=0; j<w; j++) {
            printf("%d%c",block[i][j],j==w-1?'\n':' ');
        }*/
        if (dfs(xs,ys)) puts("OK");
        else puts("NG");
    }
}

C++: #include <iostream>
#include <exception>

using namespace std;

int table[100][100];
int memo[100][100];

int w, h;
int xs, ys, xg, yg;
int n;

void solve(int xs, int ys, int c)
{
	if( memo[xs][ys] ) {
		return;
	}

	if( !( 0 < xs && xs < w+1 && 0 < ys && ys < h+1 && table[xs][ys] == c ) ) {
		memo[xs][ys] = 1;
		return;
	}
	
	if( xs == xg && ys == yg ) {
		memo[xs][ys] = 1;
		throw string("OK");
	}

	memo[xs][ys] = 1;	

	solve(xs+1, ys, c);
	solve(xs, ys+1, c);	
	solve(xs-1, ys, c);
	solve(xs, ys-1, c);

	return;
}

int main(int argc, char* argv[])
{
	while(1) {

		for( int i = 0; i < 100; i++ ) {
			for( int j = 0; j < 100; j++ ) {
				table[i][j] = 0;
				memo[i][j] = 0;
			}
		}		

		cin >> w >> h;

		if( w == 0 && h == 0 )
			break;
			
		cin >> xs >> ys;
		cin >> xg >> yg;
		cin >> n;

		for( int i = 0; i < n; i++ ) {

			int c; cin >> c;
			int d; cin >> d;
			int x, y; cin >> x >> y;

			table[x][y] = c;
			table[x][y+1] = c;
			table[x+1][y] = c;
			table[x+1][y+1] = c;

			if( d == 0 ) {

				table[x+2][y] = c;
				table[x+2][y+1] = c;
				table[x+3][y] = c;
				table[x+3][y+1] = c;																

			} else {

				table[x][y+2] = c;
				table[x+1][y+2] = c;
				table[x][y+3] = c;
				table[x+1][y+3] = c;								
			}
		}

		try {
			if( table[xs][ys] )
				solve(xs, ys, table[xs][ys]);
			cout << "NG" << endl;
		} catch(string& msg) {
			cout << msg << endl;
		}
	}

    return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <complex>
#include <cstring>
#include <cstdlib>
#include <string>
#include <cmath>
#include <queue>
using namespace std;

#define REP(i,n) for(int i=0;i<(int)n;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
const int INF = 1<<30;

typedef pair<int,int> pii;

int w,h;
int xs, ys, xg, yg;
int ba[100][100];

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

bool solve() {
  queue<pii> Q;
  bool visited[w][h];
  memset(visited, 0, sizeof(visited));
  Q.push(pii(xs,ys));
  int col = ba[xs][ys];
  while(Q.size()){
    pii a = Q.front();
    int x = a.first, y = a.second;
    Q.pop();
//    printf("%d %d   %d\n", x,y, visited[x][y]);
    visited[x][y] = 1;
    REP(k,4) {
      int xx = x + dx[k];
      int yy = y + dy[k];
      //    cout << " " <<x << endl;
      if (xx<0 || w<=xx || yy<0 || h<=yy) continue;
      if (visited[xx][yy]) continue;
      if (col != ba[xx][yy]) continue;
      
      if (xx == xg && yy == yg)
        return true;
      //cout << xx << ". " << yy << endl;
      Q.push(pii(xx,yy));
    }
  }
  return false;
}

int main() {
  while(cin>>w>>h,w+h) {
    cin >>xs>>ys>>xg>>yg;
    xs--;ys--;xg--;yg--;
    int n;
    cin >> n;
    REP(i,n) {
      int c,d,x,y;
      cin >> c>>d>>x>>y;
      x--;y--;
      REP(i,8) {
        if (d==0)
          ba[x+i%4][y+i/4] = c;
        else
          ba[x+i/4][y+i%4] = c;
      }
    }
    // REP(y,h) {
    //   REP(x,w)
    //     cout << ba[x][y] << " ";
    //   cout << endl;
    // }
    if (solve())
      cout << "OK" << endl;
    else
      cout << "NG" << endl;
  }
}