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 <iostream>
# include <queue>
# define MAX_H 50
# define MAX_W 50

typedef std::pair<int, int> P;

int w, h;
int tx, ty, kx, ky;
int board[MAX_H][MAX_W];

int dtx[4] = { 1,-1,0,0 }, dty[4] = { 0,0,1,-1 };
int dkx[4] = { -1,1,0,0 }, dky[4] = { 0,0 - 1,1 };

struct Points {
	P t, k;
	int c;
	Points( P _t, P _k, int _c) : t(_t), k(_k), c(_c) {}
};

int bfs() {
	std::queue<Points> que;
	que.push(Points(P(tx, ty), P(kx, ky), 0));
	while (!que.empty()) {
		P t = que.front().t, k = que.front().k;
		int c = que.front().c;
		que.pop();
		if (c >= 100)
			return -1;
		for (int i = 0; i < 4; ++i) {
			int ntx = t.first + dtx[i];
			int nty = t.second + dty[i];
			int nkx = k.first + dkx[i];
			int nky = k.second + dky[i];
			if (ntx == nkx&&nty == nky)
				return c;
			bool t_flag = (0 <= ntx && 0 <= nty&&ntx < w&&nty < h&&!board[nty][ntx]);
			bool k_flag = (0 <= nkx && 0 <= nky&&nkx < w&&nky < h&&!board[nky][nkx]);
			if (t_flag&&k_flag)
				que.push(Points(P(ntx, nty), P(nkx, nky), c + 1));
			else if (!t_flag&&k_flag)
				que.push(Points(t, P(nkx, nky), c + 1));
			else if (t_flag&&!k_flag)
				que.push(Points(P(ntx, nty), k, c + 1));
			else
				continue;
		}
	}
	return -1;
}

int main() {
	while (1) {
		std::cin >> w >> h;
		if (w == 0 && h == 0)
			break;
		std::cin >> tx >> ty >> kx >> ky;
		for (int i = 0; i < h; ++i) {
			for (int j = 0; j < w; ++j) {
				std::cin >> board[i][j];
			}
		}
		if (bfs() == -1)
			std::cout << "NA" << std::endl;
		else
			std::cout << bfs() << std::endl;
	}
	return 0;
}

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);
		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)ntx=tx,nty=ty;
				if(nkx<0||nkx>=w||nky<0||nky>=h)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;
}