Go: package main

import (
	"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.Init(&pq)
	//heap.Push(&pq, start)
	pq.Push(start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]int64, 0)
	ans := int64(101)
	for pq.Len() > 0 {
		//now := heap.Pop(&pq).(*Status)
		now := pq.Pop().(*Status)
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if v, ok := memo[now.Person]; ok && v <= now.Turn {
			continue
		}
		memo[now.Person] = now.Turn
		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)
				pq.Push(next)
			}
		}
	}
	if ans == 101 {
		fmt.Println("NA")
	} else {
		fmt.Println(ans)
	}
}

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

C++: /*#include<cstdio>
#include<iostream>
#include<algorithm>
#include<math.h>
#include<queue>
#include<string.h>
#include<string>
#include<vector>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
struct X
{
int tx, ty, t, kx, ky;
};
int java[51][51][51][51] = { 0 };
int main()
{
int w, h, map[52][52] = { 0 };
int mx[4] = { 0,1,0,-1 }, my[4] = { 1,0,-1,0 };
while (1)
{
queue<X> que;
X c;
cin >> w >> h;
if (w == 0 && h == 0)
break;
memset(java, 0, sizeof(java));
memset(map,0,sizeof(map));
cin >> c.tx >> c.ty >> c.kx >> c.ky;
c.t = 0;
que.push(c);
rep1(i, h)
{
rep1(j, w)
{
cin >> map[i][j];
}
}
for(int i=0;i<=h+1;i++)
{
map[i][0] = 1;
map[i][w + 1] = 1;
}
for(int i=0;i<=w+1;i++)
{
map[0][i] = 1;
map[h + 1][i] = 1;
}
while (!que.empty())
{
c = que.front();
que.pop();
cout<<"T "<<map[c.tx][c.ty]<<' '<<c.tx<<' '<<c.ty<<"K "<<map[c.kx][c.ky]<<' '<<c.kx<<' '<<c.ky<<endl;
java[c.tx][c.ty][c.kx][c.ky] = 1;
if (c.tx == c.kx&&c.ty == c.ky||c.t >= 100)
{
cout << "FACKYOU!" << endl;
break;
}
c.t++;
rep(i, 4)
{
if (java[c.tx + mx[i]][c.ty + my[i]][c.kx - mx[i]][c.ky - my[i]] == 0 && map[c.tx + mx[i]][c.ty + my[i]] == 0 && map[c.kx - mx[i]][c.ky - my[i]] == 0)
{
c.tx += mx[i];
c.ty += my[i];
c.kx -= mx[i];
c.ky -= my[i];
que.push(c);
java[c.tx][c.ty][c.kx][c.ky] = 1;
c.tx -= mx[i];
c.ty -= my[i];
c.kx += mx[i];
c.ky += my[i];
}
else if (java[c.tx][c.ty][c.kx - mx[i]][c.ky - my[i]] == 0 && map[c.tx + mx[i]][c.ty + my[i]] == 1 && map[c.kx - mx[i]][c.ky - my[i]] == 0)
{
c.kx -= mx[i];
c.ky -= my[i];
que.push(c);
java[c.tx][c.ty][c.kx][c.ky] = 1;
c.kx += mx[i];
c.ky += my[i];
}
else if (java[c.tx + mx[i]][c.ty + my[i]][c.kx][c.ky] == 0 && map[c.tx + mx[i]][c.ty + my[i]] == 0 && map[c.kx - mx[i]][c.ky - my[i]] == 1)
{
c.tx += mx[i];
c.ty += my[i];
que.push(c);
java[c.tx][c.ty][c.kx][c.ky] = 1;
c.tx -= mx[i];
c.ty -= my[i];
}
}
}
if (c.tx==c.kx&&c.ky==c.ty)
cout << c.t << endl;
else
cout << "NA" << endl;
}
return 0;
}*/
#include<stdio.h>
#include<iostream>
#include<queue>
#include<string.h>
using namespace std;
struct Y{
int hx,hy,rx,ry,t;
};
int c[51][51][51][51],mp[52][52];
int main(){
int w,h,i,j,a[2]={1,-1},b[2];
Y e;
while(1){
queue<Y> q;
cin>>w>>h;
if(w==0&&h==0)break;
cin>>e.hx>>e.hy>>e.rx>>e.ry;
e.t=0;
q.push(e);
memset(c,0,sizeof(c));
memset(mp,-1,sizeof(mp));
for(i=1;i<=h;i++){
for(j=1;j<=w;j++){
cin>>mp[i][j];
}
}
while(!q.empty()){
e=q.front();
q.pop();
c[e.hy][e.hx][e.ry][e.rx]=1;
if(e.t>=100||e.hx==e.rx&&e.hy==e.ry)break;
e.t++;
for(i=0;i<2;i++){
if(mp[e.hy+a[i]][e.hx]==0&&c[e.hy+a[i]][e.hx][e.ry-a[i]][e.rx]==0&&mp[e.ry-a[i]][e.rx]==0||mp[e.ry-a[i]][e.rx]==0&&c[e.hy][e.hx][e.ry-a[i]][e.rx]==0&&mp[e.hy+a[i]][e.hx]!=0||mp[e.hy+a[i]][e.hx]==0&&mp[e.ry-a[i]][e.rx]!=0&&c[e.hy+a[i]][e.hx][e.ry][e.rx]==0){
b[0]=0;
b[1]=0;
if(mp[e.hy+a[i]][e.hx]==0){
e.hy+=a[i];
b[0]=1;
}
if(mp[e.ry-a[i]][e.rx]==0){
e.ry-=a[i];
b[1]=1;
}
c[e.hy][e.hx][e.ry][e.rx]=1;
q.push(e);
if(b[0]==1)e.hy-=a[i];
if(b[1]==1)e.ry+=a[i];
}
if(mp[e.hy][e.hx+a[i]]==0&&mp[e.ry][e.rx-a[i]]==0&&c[e.hy][e.hx+a[i]][e.ry][e.rx-a[i]]==0||mp[e.hy][e.hx+a[i]]==0&&c[e.hy][e.hx+a[i]][e.ry][e.rx]==0&&mp[e.ry][e.rx-a[i]]!=0||mp[e.ry][e.rx-a[i]]==0&&mp[e.hy][e.hx+a[i]]!=0&&c[e.hy][e.hx][e.ry][e.rx-a[i]]==0){
b[0]=0;
b[1]=0;
if(mp[e.hy][e.hx+a[i]]==0){
e.hx+=a[i];
b[0]=1;
}
if(mp[e.ry][e.rx-a[i]]==0){
e.rx-=a[i];
b[1]=1;
}
c[e.hy][e.hx][e.ry][e.rx]=1;
q.push(e);
if(b[0]==1)e.hx-=a[i];
if(b[1]==1)e.rx+=a[i];
}
}
e.t--;
}
if(e.hy==e.ry&&e.hx==e.rx)cout<<e.t<<endl;
else cout<<"NA"<<endl;
}
return 0;
}