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 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)
	pq = append(pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]int64, 0)
	ans := int64(102)
	for len(pq) > 0 {
		now := pq[0]
		pq = pq[1:]
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if ans <= now.Turn {
			continue
		}

		if _, ok := memo[now.Person]; ok {
			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++
			if next.Turn <= 100 {
				pq = append(pq, next)
			}
		}
	}
	if ans == 102 {
		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 <set>
#include <queue>
#include <cstring>
using namespace std;
typedef pair<int,int> pos;
typedef pair<pos,pos> two;
typedef pair<int,two> node;
int map[52][52];
int next[4][4] = {
  { 1, 0, -1, 0 },
  {-1, 0,  1, 0 },
  { 0, 1,  0,-1 },
  { 0,-1,  0, 1 },
};
int main()
{
  for(;;){
    int x,y,tx,ty,kx,ky;
    scanf("%d %d",&x,&y);
    if(x == 0 || y == 0) break;
    memset(map,0,sizeof(map));
    scanf("%d %d",&tx,&ty);
    scanf("%d %d",&kx,&ky);
    set<two> memo;
    two t = make_pair(make_pair(tx,ty),make_pair(kx,ky));
    memo.insert(t);
    queue<node> q;
    node n = make_pair(0,t);
    q.push(n);
    int i,j;
    for(i=1; i<=y; i++){
      for(j=1; j<=x; j++){
        int n;
        scanf("%d",&n);
        map[i][j] = n;
      }
    }
    for(;;){
      if(q.empty()){
        printf("NA\n");
        break;
      }
      node n = q.front();
      q.pop();
      if(n.first > 100){
        printf("NA\n");
        break;
      }
      pos t = n.second.first;
      pos k = n.second.second;
      if(t == k){
        printf("%d\n",n.first);
        break;
      }
      two temp;
      for(int i=0; i<4; i++){
        pos tn = make_pair(t.first+next[i][0], t.second+next[i][1]);
        pos kn = make_pair(k.first+next[i][2], k.second+next[i][3]);
        bool bt = true, bk = true;
        if(tn.second == 0 || tn.second > y || tn.first == 0 || tn.first > x ||
           map[tn.second][tn.first] == 1) bt = false;
        if(kn.second == 0 || kn.second > y || kn.first == 0 || kn.first > x ||
           map[kn.second][kn.first] == 1) bk = false;
        if(!bt && !bk){
          continue;
        }else if(!bt){
          temp = make_pair(t,kn);
        }else if(!bk){
          temp = make_pair(tn,k);
        }else{
          temp = make_pair(tn,kn);
        }
        if(memo.insert(temp).second){
          node nd = make_pair(n.first+1,temp);
          q.push(nd);
        }
      }
    }
  }
  return 0;
}

C++: #include <iostream>
#include <map>
#include <queue>
#include <algorithm>
using namespace std;
typedef pair<int,int> P;

int w,h,ans;
int a[51][51];
bool f[51][51][51][51];
int dx[4] = {0,0,1,-1};
int dy[4] = {1,-1,0,0};

struct cost{
	P tp,kp;
	int cnt;
};

void solve(struct cost c){
	queue<struct cost> q;
	q.push( c );
	ans = -1;
	for(int ty=0 ; ty < h ; ty++ ){
		for(int tx=0 ; tx < w ; tx++ ){
			for(int ky=0 ; ky < h ; ky++ ){
				for(int kx=0 ; kx < w ; kx++ ){
					f[ty][tx][ky][kx] = false;
				}
			}
		}
	}

	while( !q.empty() ){
		struct cost now = q.front(), next;
		q.pop();
		int tx = now.tp.first;
		int ty = now.tp.second;
		int kx = now.kp.first;
		int ky = now.kp.second;
		next.cnt = now.cnt + 1;
		if( f[ty][tx][ky][kx] ){
			continue;
		}else{
			f[ty][tx][ky][kx] = true;
		}
		if( now.cnt == 100 ){
			break;
		}
		if( tx == kx && ty == ky ){
			ans = now.cnt;
			break;
		}

		for(int i=0 ; i < 4 ; i++ ){
			int tmx = tx + dx[i];
			int tmy = ty + dy[i];
			int kmx = kx - dx[i];
			int kmy = ky - dy[i];
			if( tmx < 0 || tmy < 0 || tmx >= w || tmy >= h || a[tmy][tmx] ){
				P tp(tx,ty);
				next.tp = tp;
			}else{
				P tp(tmx,tmy);
				next.tp = tp;
			}
			if( kmx < 0 || kmy < 0 || kmx >= w || kmy >= h || a[kmy][kmx] ){
				P kp(kx,ky);
				next.kp = kp;
			}else{
				P kp(kmx,kmy);
				next.kp = kp;
			}
			q.push( next );
		}
	}
}

int main(){
	while( cin >> w >> h , w||h ){
		int tx, ty, kx, ky;
		cin >> tx >> ty >> kx >> ky;
		tx--; ty--; kx--; ky--;
		for(int y=0 ; y < h ; y++ ){
			for(int x=0 ; x < w ; x++ ){
				cin >> a[y][x];
			}
		}

		struct cost c;
		P tp(tx,ty), kp(kx,ky);
		c.tp = tp;
		c.kp = kp;
		c.cnt = 0;
		solve( c );
		if( ans == -1 ){
			cout << "NA" << endl;
		}else{
			cout << ans << endl;
		}
	}
}