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.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<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 check(int, int, int, int, int, int, int, int);

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,as;
			cin >> w >> h;
			if (w == 0 && h == 0)
				break;
			memset(java, 0, sizeof(java));
			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];
				}
			}
			/*?£???????*/
			rep(i, h + 2)//n???????????°,m????¨??????°
			{
				map[i][0] = 1;
				map[i][w + 1] = 1;
			}
			rep(i, w + 2)
			{
				map[0][i] = 1;
				map[h + 1][i] = 1;
			}
			while (!que.empty())
			{
				c = que.front();
				que.pop();
				java[c.tx][c.ty][c.kx][c.ky] = 1;
				if (c.tx == c.kx&&c.ty == c.ky||c.t >= 100)
				{
					break;
				}
				c.t++;
				as = c;
				rep(i, 4)
				{
					if (check(c.tx, c.ty, c.kx, c.ky, mx[i], my[i], h, w))
					{
						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)
						{
							as.tx = c.tx + mx[i];
							as.ty = c.ty + my[i];
							as.kx = c.kx - mx[i];
							as.ky = c.ky - my[i];
							que.push(as);
							java[as.tx][as.ty][as.kx][as.ky] = 1;
						}
						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]] != 0 && map[c.kx - mx[i]][c.ky - my[i]] == 0)
						{
							as.kx = c.kx - mx[i];
							as.ky = c.ky - my[i];
							que.push(as);
							java[as.tx][as.ty][as.kx][as.ky] = 1;
						}
						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]] != 0)
						{
							as.tx = c.tx + mx[i];
							as.ty = c.ty + my[i];
							que.push(as);
							java[as.tx][as.ty][as.kx][as.ky] = 1;
						}
					}
				}
			}
			if (c.tx == c.kx&&c.ty == c.ky)
				cout << c.t << endl;
			else
				cout << "NA" << endl;
		}
	return 0;
}


int check(int tx, int ty, int kx, int ky, int mx, int my ,int h ,int w )
{
	if (tx > w || kx > w || ty > h || ky > h || tx < 1 || kx < 1 || ty < 1 || ky < 1)
	{
		return 0;
	}

	return 1;
}

C++: #include<iostream>
#include<sstream>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<algorithm>
#include<numeric>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<cassert>

#define rep(i,n) for(int i=0;i<n;i++)
#define all(c) (c).begin(),(c).end()
#define mp make_pair
#define pb push_back
#define rp(i,c) rep(i,(c).size())
#define fr(i,c) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();i++)
#define dbg(x) cerr<<#x<<" = "<<(x)<<endl

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pi;
const int inf=1<<28;
const double INF=1e12,EPS=1e-9;

int dy[]={-1,0,1,0},dx[]={0,-1,0,1};
int w,h,tx,ty,kx,ky;
int f[50][50];
bool v[50][50][50][50];

int main()
{
	while(scanf("%d%d",&w,&h),w)
	{
		scanf("%d%d%d%d",&tx,&ty,&kx,&ky);
		tx--; ty--; kx--; ky--;
		rep(i,h)rep(j,w)scanf("%d",f[i]+j);
		rep(i,h)rep(j,w)rep(k,h)rep(l,w)v[i][j][k][l]=0;
		
		v[tx][ty][kx][ky]=1;
		queue<pair<pair<pi,pi>,int> >Q;
		Q.push(mp(mp(mp(tx,ty),mp(kx,ky)),0));
		while(!Q.empty())
		{
			tx=Q.front().first.first.first; ty=Q.front().first.first.second;
			kx=Q.front().first.second.first; ky=Q.front().first.second.second;
			int cc=Q.front().second; Q.pop();
			
			rep(d,4)
			{
				int ntx=tx+dx[d],nty=ty+dy[d];
				int nkx=kx-dx[d],nky=ky-dy[d];
				
				if(ntx<0||ntx>=w||nty<0||nty>=h||f[nty][ntx])ntx=tx,nty=ty;
				if(nkx<0||nkx>=w||nky<0||nky>=h||f[nky][nkx])nkx=kx,nky=ky;
				if(v[ntx][nty][nkx][nky]||cc>=99)continue;
				if(ntx==nkx&&nty==nky)
				{
					printf("%d\n",cc+1); goto END;
				}
				Q.push(mp(mp(mp(ntx,nty),mp(nkx,nky)),cc+1));
				v[ntx][nty][nkx][nky]=1;
			}
		}
		puts("NA"); END:;
	}
	return 0;
}