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)
	pq = append(pq, 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)
		now := pq[0]
		pq = pq[1:]
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if ans <= now.Turn {
			continue
		}
		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)
				pq = append(pq, 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 <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>

using namespace std;

#define rep(i,j) REP((i), 0, (j))
#define REP(i,j,k) for(int i=(j);(i)<(k);++i)
#define BW(x,b) ((x)>=0&&(x)<(b))
#define Y first
#define X second
#define INF 1 << 30

typedef pair<int, int> pii;
typedef queue<int> qi;
typedef pair<int, int> pi;

int board[51][51], Y, X;
int dx[] = {0,1,0,-1}, dy[] = {1,0,-1,0};

pii nextp(pii now, int i, int d){
  pii next = now;
  next.Y += dy[i] * d;
  next.X += dx[i] * d;
  if(BW(next.Y, Y) && BW(next.X, X) && board[next.Y][next.X] == 0) return next;
  return now;
}
     
int main(){
  while(scanf("%d%d", &X,  &Y) && X+Y){
    int tx, ty, kx, ky;
    scanf("%d%d%d%d", &tx, &ty, &kx, &ky); tx--; ty--; kx--; ky--;
    rep(i, Y) rep(j, X) scanf("%d", &board[i][j]); 

    map<pair<pi,pi>, bool>m; // t k
    queue<pii>tq, kq;
    tq.push(make_pair(ty, tx));
    kq.push(make_pair(ky, kx));
    m[make_pair(make_pair(ty, tx), make_pair(ky, kx))] = 1;
    int res = 1;
    while(!tq.empty()){
      if(res >= 100) break;
      int qsize = (int)tq.size();
      rep(i, qsize){
	pii t = tq.front(); tq.pop();
	pii k = kq.front(); kq.pop();
	rep(j, 4){
	  pii nt = nextp(t, j, 1), nk = nextp(k, j, -1);
	  pair<pi, pi> next = make_pair(make_pair(nt.Y, nt.X), make_pair(nk.Y, nk.X));
	  if(m.count(next) == 1) continue;
	  if(nt == nk){
	    printf("%d\n", res);
	    goto end;
	  }
	  m[next] = 1;
	  tq.push(nt); kq.push(nk);
	}
      }
      res++;

    }
    puts("NA");
  end:;
  }
  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,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);
			for( int i = 1 ; i <= h ; ++i )//rep1(i, h)
			{
				for( int j = 1 ; j <= w ; ++j )//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 (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;
}