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)
	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.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 {
		heap.Init(&pq)
		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<stdio.h>
#include<queue>
using namespace std;
queue<int> tx, ty, kx, ky;
int d[50][50];
int sa[50][50][50][50];
void move(void);
void clean(void);
int main(void)
{
	int x, y, X, Y,i,j;
	while (1) {
		for (i = 0; i < 50; i++) {
			for (j = 0; j < 50; j++) {
				d[i][j] = 1;
			}
		}
		scanf("%d %d", &X, &Y);   //????????????
		if (X == 0 && Y == 0) break;
		scanf("%d %d", &x, &y);   //????????????
		tx.push(x);  ty.push(y);
		scanf("%d %d", &x, &y);   //????????????
		kx.push(x);  ky.push(y);
		for (i = 1; i <= Y; i++) {
			for (j = 1; j <= X; j++) {
				scanf("%d", &d[i][j]);
			}
		}
		move();
		clean();
	}
	return 0;
}

void move()
{
	int cnt = 0,count=0,s=1;
	int m[4][4]={-1,1,0,0,      //taka y
				 0,0,-1,1,      //taka x
				 1,-1,0,0,      //kazu y
				 0,0,1,-1};     //kazu x
	while (1) {
		if (tx.back() == kx.back() && ty.back() == ky.back()) {
			printf("A%d\n", count);
			break;
		}
		if(sa[tx.front() + m[1][cnt%4]] [ty.front() + m[0][cnt%4]] [kx.front() + m[3][cnt%4]] [ky.front() + m[2][cnt%4]] != 1){
		if (d[ty.front() + m[0][cnt%4]][tx.front() + m[1][cnt%4]] == 0) {              //?????????
			tx.push(tx.front() + m[1][cnt%4]);
			ty.push(ty.front() + m[0][cnt%4]);
		}
		else if (d[ty.front() + m[0][cnt%4]][tx.front() + m[1][cnt%4]] == 1) {
			tx.push(tx.front());
			ty.push(ty.front());
		}
		if (d[ky.front() + m[2][cnt%4]][kx.front() + m[3][cnt%4]] == 0) {              //?????????
			kx.push(kx.front() + m[3][cnt%4]);
			ky.push(ky.front() + m[2][cnt%4]);
		}
		else if (d[ky.front() + m[2][cnt%4]][kx.front() + m[3][cnt%4]] == 1) {
			kx.push(kx.front());
			ky.push(ky.front());
		}
		}
		else{printf("AAA");}
		printf("%d ??????x.%d y.%d   ??????x.%d y.%d\n",cnt%4, tx.back(),ty.back(), kx.back(),ky.back());
		sa[tx.back()][ty.back()][kx.back()][ky.back()] = 1;
		cnt++;
		if(cnt == 1 && count == 0) count++;
		if(cnt == s*4){
			count++;
			s = s * 4;
			cnt = 0;
			printf("\nQQQ\n");
		}
		//printf("%d ??????x.%d y.%d   ??????x.%d y.%d\n",cnt%4, tx.back(),ty.back(), kx.back(),ky.back());
		//printf("X %d %d\nY %d %d",kx.front(),m[3][cnt%4],ky.front(),m[2][cnt%4]);
		if (tx.back() == kx.back() && ty.back() == ky.back()) {
			printf("%d\n", count);
			break;
		}
	
		if(cnt % 4 == 0 && cnt !=0){
			tx.pop();  ty.pop();  kx.pop();  ky.pop();
			printf("///");
		}
		if (count >= 100) {
			printf("NA\n");
			break;
		}
	}
}

void clean(void)
{
	while (!tx.empty()) {
		tx.pop();
	}
	while (!ty.empty()) {
		ty.pop();
	}
	while (!kx.empty()) {
		kx.pop();
	}
	while (!ky.empty()) {
		ky.pop();
	}
}
*/

#include<stdio.h>
#include<string.h>
#include<queue>
using namespace std;

struct AO
{
	int tx;
	int ty;
	int kx;
	int ky;
	int cnt;
};

queue<AO> Q;
AO TK,f;
int d[51][51];
int sa[51][51][51][51];

int main()
{
	int X,Y,F; //     tx ty kx ky
	int mv[4][4] ={{ 0,-1, 0, 1}, //???
				   { 0, 1, 0,-1}, //???
				   {-1, 0, 1, 0}, //???
				   { 1, 0,-1, 0}};//???
	while(1){
		F = 1;
		for(int i=0;i<52;i++){
			for(int j=0;j<52;j++){
				d[i][j] = 1;
			}
		}
		memset(sa,0,sizeof(sa));
		//printf("%d\n",d[0][0]);
		scanf("%d %d",&X,&Y);
		if(X == 0 && Y == 0) break;
		scanf("%d %d %d %d",&TK.tx,&TK.ty,&TK.kx,&TK.ky);
		sa[TK.ty][TK.tx][TK.ky][TK.kx] = 1;
		TK.cnt = 0;
		Q.push(TK);
		for(int i=1;i<=Y;i++){
			for(int j=1;j<=X;j++){
				scanf("%d",&d[i][j]);
			}
		}

		while(!Q.empty()){    //!Q.empty()
			TK = Q.front();
			Q.pop();
			//printf("?????? ??????:%d %d  ??????:%d %d\n",TK.tx,TK.ty,TK.kx,TK.ky);
			if(TK.cnt >= 100){
				break;
			}
			if(TK.tx == TK.kx && TK.ty == TK.ky){
				F = 0;
				break;
			}
			if(TK.cnt >= 100){
				break;
			}
			for(int i=0;i<4;i++){
				f.tx = TK.tx + mv[i][0];
				f.ty = TK.ty + mv[i][1];
				f.kx = TK.kx + mv[i][2];
				f.ky = TK.ky + mv[i][3];
				f.cnt = TK.cnt + 1;
				//printf("A");
				if(d[f.ty][f.tx] == 0 || d[f.ky][f.kx] == 0){
					if(d[f.ty][f.tx] == 1){
						f.tx = TK.tx;
						f.ty = TK.ty;
					}
					if(d[f.ky][f.kx] == 1){
						f.kx = TK.kx;
						f.ky = TK.ky;
					}
				}
				else if(d[f.ty][f.tx] == 1 && d[f.ky][f.kx] == 1){
					continue;
				}
				if(  sa[f.ty][f.tx][f.ky][f.kx] == 1 || f.tx < 0 || f.kx < 0 || f.ty < 0 || f.ky < 0 || f.tx > X || f.kx > X || f.ty > Y || f.ky > Y){
					continue;
				}
				sa[f.ty][f.tx][f.ky][f.kx] = 1;
				Q.push(f);
				//printf("??????%d %d\n?????? %d %d\n",f.tx,f.ty,f.kx,f.ky);
			}
			//printf("------------\n");
		}
		if(F==0)
			printf("%d\n",TK.cnt);
			//printf("%d %d %d %d\n",TK.tx,TK.ty,TK.kx,TK.ky);
		else
			printf("NA\n");
		while(!Q.empty())
			Q.pop();
	}
	return 0;
}