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
		}
		if ans<=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<bits/stdc++.h>
#define INF (1e9)
#define s second
#define f first
#define N 50
using namespace std;
typedef pair<int,int> P;
typedef pair<P,P> P1;
typedef pair<int,P1> P2;
int x,y,stx,sty,skx,sky;
int d[N][N][N][N];
int dat[N][N];
int dy[4]={-1,0,1,0};
int dx[4]={0,1,0,-1};

int bfs(){
  queue<P2> q;
  d[sty][stx][sky][skx]=0;
  q.push(P2(0,P1(P(sty,stx),P(sky,skx))));
  while(!q.empty()){
    P2 t=q.front(); q.pop();
    int cost=t.f;
    int ty=t.s.f.f,tx=t.s.f.s;
    int ky=t.s.s.f,kx=t.s.s.s;
    if(d[ty][tx][ky][kx]<cost)continue;
    if(ty==ky&&tx==kx)return cost;
    for(int i=0;i<4;i++){
      int nty=ty+dy[i],ntx=tx+dx[i];
      int nky=ky-dy[i],nkx=kx-dx[i];
      if(nty<0||ntx<0||y<=nty||x<=ntx)
	nty=ty,ntx=tx;
      else if(dat[nty][ntx])
	nty=ty,ntx=tx;
      if(nky<0||nkx<0||y<=nky||x<=nkx)
	nky=ky,nkx=kx;
      else if(dat[nky][nkx])
	nky=ky,nkx=kx;
      if(d[nty][ntx][nky][nkx]>cost+1){
	d[nty][ntx][nky][nkx]=cost+1;
	q.push(P2(cost+1,P1(P(nty,ntx),P(nky,nkx))));
      }
    }
  }
  return -1;
}

int main(){
  while(1){
    cin>>x>>y;
    if(!x&&!y)break;
    cin>>stx>>sty>>skx>>sky;
    for(int i=0;i<y;i++)
      for(int j=0;j<x;j++)
	cin>>dat[i][j];
    for(int i=0;i<y;i++)
      for(int j=0;j<x;j++)
	for(int k=0;k<y;k++)
	  for(int l=0;l<x;l++)
	    d[i][j][k][l]=INF;
    int ans=bfs();
    if(ans==-1)cout<<"NA"<<endl;
    else cout<<ans<<endl;

  }
  return 0;
}

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));
			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++;
				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]] != 0 && 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]] != 0)
					{
						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.ty == c.ky)
				cout << c.t << endl;
			else
				cout << "NA" << endl;
		}
	return 0;
}

C++: #include <iostream>
#include <cstring>
#include <queue>
#include <map>
#define fr first
#define sc second
using namespace std;

typedef pair<int, int> iP;
typedef pair<iP, iP> iiP;
typedef pair<iiP, int> iiiP;

int w, h;
iP ts, ks;
int mas[51][51], used[51][51][51][51];
int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};

int bfs(){
  
  memset(used, -1, sizeof(used));
  queue <iiiP> que;
  que.push(iiiP(iiP(ts, ks), 0)); used[ts.fr][ts.sc][ks.fr][ks.sc] = 0;
  while(!que.empty()){
    iiiP p = que.front(); que.pop();
    if(p.fr.fr == p.fr.sc){
      if(p.sc >= 100) return -1;
      else return p.sc;
    }
    int tx = p.fr.fr.fr, ty = p.fr.fr.sc, kx = p.fr.sc.fr, ky = p.fr.sc.sc;
    for(int i = 0; i < 4; i++){
      int ntx = tx + dx[i], nty = ty + dy[i];
      int nkx = kx - dx[i], nky = ky - dy[i];
      if(~used[ntx][nty][nkx][nky]) continue;
      if(ntx >= 0 && ntx < w && nty >= 0 && nty < h && nkx >= 0 && nkx < w && nky >= 0 && nky < h && 
	 used[ntx][nty][nkx][nky] < used[tx][ty][kx][ky] + 1){
	que.push(iiiP(iiP(iP(ntx, nty), iP(nkx, nky)), p.sc + 1));
	used[ntx][nty][nkx][nky] = used[tx][ty][kx][ky] + 1;
      }
    }
  }
  return -1;

}  

int main(){
  
  while(cin >> w >> h, w||h){
    cin >> ts.fr >> ts.sc;
    cin >> ks.fr >> ks.sc;
    for(int i = 0; i < h; i++){
      for(int j = 0; j < w; j++) cin >> mas[i][j];
    }

    int ans = bfs();
    if(ans == -1) cout << "NA" << endl;
    else cout << ans << endl;
  }

}