Go: package main

import (
	"container/heap"
	"fmt"
	"math"
)

type Position struct {
	X int64
	Y int64
}

func (one Position) Distance(another Position) int64 {
	return int64(math.Abs(float64(one.X-another.X)) + math.Abs(float64(one.Y-another.Y)))
}

type PersonPosition struct {
	Takayuki Position
	Kazuyuki Position
}

func (one PersonPosition) Distance() int64 {
	return one.Takayuki.Distance(one.Kazuyuki)
}

type Status struct {
	Person PersonPosition
	Turn   int64
}

type PQStatus []*Status

func (pq PQStatus) Len() int {
	return len(pq)
}
func (pq PQStatus) Less(i, j int) bool {
	if pq[i].Turn == pq[j].Turn {
		return pq[i].Person.Distance() < pq[j].Person.Distance()
	}
	return pq[i].Turn < pq[j].Turn
}

func (pq PQStatus) Swap(i, j int) {
	pq[i], pq[j] = pq[j], pq[i]
}

func (pq *PQStatus) Push(x interface{}) {
	item := x.(*Status)
	*pq = append(*pq, item)
}

func (pq *PQStatus) Pop() interface{} {
	old := *pq
	n := len(old)
	item := old[n-1]
	*pq = old[0 : n-1]
	return item
}

func solve(h, w int64) {
	var tx, ty, kx, ky int64
	fmt.Scan(&tx, &ty, &kx, &ky)
	m := make([][]int64, h)
	for i := range m {
		m[i] = make([]int64, w)
		for j := int64(0); j < w; j++ {
			fmt.Scan(&m[i][j])
		}
	}
	start := &Status{Person: PersonPosition{Takayuki: Position{X: tx, Y: ty}, Kazuyuki: Position{X: kx, Y: ky}}, Turn: 0}
	pq := make(PQStatus, 0)
	heap.Init(&pq)
	heap.Push(&pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		for i := 0; i < 4; i++ {
			next := &Status{}
			*next = *now
			next.Person.Kazuyuki.X += dx[i]
			next.Person.Kazuyuki.Y += dy[i]
			if next.Person.Kazuyuki.X < 0 || next.Person.Kazuyuki.X >= w ||
				next.Person.Kazuyuki.Y < 0 || next.Person.Kazuyuki.Y >= h ||
				m[next.Person.Kazuyuki.Y][next.Person.Kazuyuki.X] == 1 {
				next.Person.Kazuyuki.X -= dx[i]
				next.Person.Kazuyuki.Y -= dy[i]
			}
			next.Person.Takayuki.X -= dx[i]
			next.Person.Takayuki.Y -= dy[i]
			if next.Person.Takayuki.X < 0 || next.Person.Takayuki.X >= w ||
				next.Person.Takayuki.Y < 0 || next.Person.Takayuki.Y >= h ||
				m[next.Person.Takayuki.Y][next.Person.Takayuki.X] == 1 {
				next.Person.Takayuki.X += dx[i]
				next.Person.Takayuki.Y += dy[i]
			}
			next.Turn += 1
			if next.Turn < 100 {
				heap.Push(&pq, next)
			}
		}
	}
	fmt.Println("NA")
}

func main() {
	var h, w int64
	for {
		fmt.Scan(&h, &w)
		if h == 0 && w == 0 {
			break
		}
		solve(h, w)
	}
}

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

int flg[51][51][51][51];

struct Twins
{
	int tax, tay;
	int kax, kay;
	int cnt;
};

queue <Twins> que;

bool check(int y1, int x1, int y2, int x2){ //?????§????????£?????¢?´¢??????


	if (flg[y1][x1][y2][x2] == 0) return true;
	return false;
}

int main(void){

	int x, y;
	int tx, ty;
	int kx, ky;
	Twins twins;

	while (cin >> x >> y && x != 0 && y != 0){

		memset(flg, 0, sizeof(flg));

		while (!que.empty())
			que.pop();
		int map[50][50];
		memset(map, 1, sizeof(map));

		cin >> tx >> ty >> kx >> ky;

		twins.cnt = 0, twins.tax = tx, twins.tay = ty, twins.kax = kx, twins.kay = ky;

		for (int i = 1; i < y + 1; i++){
			for (int j = 1; j < x + 1; j++)
					cin >> map[i][j];
		}

		que.push(twins);
		flg[que.front().tay][que.front().tax][que.front().kay][que.front().kax] = 1;

		while (1){

			if (que.front().cnt >= 100){
				break;
			}
			if (que.front().kax == que.front().tax && que.front().kay == que.front().tay){
				break;
			}

			//T????????????K?????????
			if (map[que.front().tay - 1][que.front().tax] == 0){ //T???????????????????£???????
				if (map[que.front().kay + 1][que.front().kax] == 0){ //K???????????????????£???????
					if (check(que.front().tay - 1, que.front().tax, que.front().kay + 1, que.front().kax)){
						twins.tay = que.front().tay - 1, twins.tax = que.front().tax, twins.kay = que.front().kay + 1, twins.kax = que.front().kax;
						twins.cnt = que.front().cnt + 1;
						que.push(twins);
						flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
				//		cout << "1.1" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
					}
				}
				else if (check(que.front().tay - 1, que.front().tax, que.front().kay, que.front().kax)){
					twins.tay = que.front().tay - 1, twins.tax = que.front().tax, twins.kay = que.front().kay, twins.kax = que.front().kax;
					twins.cnt = que.front().cnt + 1;
					que.push(twins);
					flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
					//cout << "1.2" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
				}
			}
			else if (map[que.front().kay + 1][que.front().kax] == 0){ //K???????????????????£???????
				if (check(que.front().tay, que.front().tax, que.front().kay + 1, que.front().kax)){
					twins.tay = que.front().tay, twins.tax = que.front().tax, twins.kay = que.front().kay + 1, twins.kax = que.front().kax;
					twins.cnt = que.front().cnt + 1;
					que.push(twins);
					flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
				//	cout << "1.3" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
				}
			}

			//T????????????K?????????
			if (map[que.front().tay + 1][que.front().tax] == 0){ //T???????????????????£???????
				if (map[que.front().kay - 1][que.front().kax] == 0){ //K???????????????????£???????
					if (check(que.front().tay + 1, que.front().tax, que.front().kay - 1, que.front().kax)){
						twins.tay = que.front().tay + 1, twins.tax = que.front().tax, twins.kay = que.front().kay - 1, twins.kax = que.front().kax;
						twins.cnt = que.front().cnt + 1;
						que.push(twins);
						flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
					//	cout << "2.1" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
					}
				}
				else if (check(que.front().tay + 1, que.front().tax, que.front().kay, que.front().kax)){
					twins.tay = que.front().tay + 1, twins.tax = que.front().tax, twins.kay = que.front().kay, twins.kax = que.front().kax;
					twins.cnt = que.front().cnt + 1;
					que.push(twins);
					flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
				//	cout << "2.2" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
				}
			}
			else if (map[que.front().kay - 1][que.front().kax] == 0){ //K???????????????????£???????
				if (check(que.front().tay, que.front().tax, que.front().kay - 1, que.front().kax)){
					twins.tay = que.front().tay, twins.tax = que.front().tax, twins.kay = que.front().kay - 1, twins.kax = que.front().kax;
					twins.cnt = que.front().cnt + 1;
					que.push(twins);
					flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
			//		cout << "2.3" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
				}
			}

			//T????????????K?????????
			if (map[que.front().tay][que.front().tax - 1] == 0){ //T???????????????????£???????
				if (map[que.front().kay][que.front().kax + 1] == 0){ //K???????????????????£???????
					if (check(que.front().tay, que.front().tax - 1, que.front().kay, que.front().kax + 1)){
						twins.tay = que.front().tay, twins.tax = que.front().tax - 1, twins.kay = que.front().kay, twins.kax = que.front().kax + 1;
						twins.cnt = que.front().cnt + 1;
						que.push(twins);
						flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
		//				cout << "3.1" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
					}
				}
				else if (check(que.front().tay, que.front().tax - 1, que.front().kay, que.front().kax)){
					twins.tay = que.front().tay, twins.tax = que.front().tax - 1, twins.kay = que.front().kay, twins.kax = que.front().kax;
					twins.cnt = que.front().cnt + 1;
					que.push(twins);
					flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
	//				cout << "3.2" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
				}
			}
			else if (map[que.front().kay][que.front().kax + 1] == 0){ //K???????????????????£???????
				if (check(que.front().tay, que.front().tax, que.front().kay, que.front().kax + 1)){
					twins.tay = que.front().tay, twins.tax = que.front().tax, twins.kay = que.front().kay, twins.kax = que.front().kax + 1;
					twins.cnt = que.front().cnt + 1;
					que.push(twins);
					flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
//					cout << "3.3" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
				}
			}

			//T????????????K?????????
			if (map[que.front().tay][que.front().tax + 1] == 0){ //T???????????????????£???????
				if (map[que.front().kay][que.front().kax - 1] == 0){ //K???????????????????£???????
					if (check(que.front().tay, que.front().tax + 1, que.front().kay, que.front().kax - 1)){
						twins.tay = que.front().tay, twins.tax = que.front().tax + 1, twins.kay = que.front().kay, twins.kax = que.front().kax - 1;
						twins.cnt = que.front().cnt + 1;
						que.push(twins);
						flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
						//cout << "4.1" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
					}
				}
				else if (check(que.front().tay, que.front().tax + 1, que.front().kay, que.front().kax)){
					twins.tay = que.front().tay, twins.tax = que.front().tax + 1, twins.kay = que.front().kay, twins.kax = que.front().kax;
					twins.cnt = que.front().cnt + 1;
					que.push(twins);
					flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
					//cout << "4.2" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
				}
			}
			else if (map[que.front().kay][que.front().kax - 1] == 0){ //K???????????????????£???????
				if (check(que.front().tay, que.front().tax, que.front().kay, que.front().kax - 1)){
					twins.tay = que.front().tay, twins.tax = que.front().tax, twins.kay = que.front().kay, twins.kax = que.front().kax - 1;
					twins.cnt = que.front().cnt + 1;
					que.push(twins);
					flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
					//cout << "4.3" << endl << twins.tax << ' ' << twins.tay << endl << twins.kax << ' ' << twins.kay << endl << endl;
				}
			}

			que.pop();
			if (que.empty())
				break;
		}

		if (que.empty() || !(que.front().kax == que.front().tax && que.front().kay == que.front().tay))
			cout << "NA" << endl;
		else
			cout << que.front().cnt << endl;

	}
}