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 _, 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 += 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 <queue>
#include <map>
using namespace std;

class Point2{
public:
  int tx;
  int ty;
  int kx;
  int ky;
};

int mk(Point2 p)
{
  return (((p.tx-1)*50+(p.ty-1))*50+(p.kx-1))*50+(p.ky-1);
}

int main()
{
  while(true){
    int W, H;
    cin >> W >> H;

    if(W==0 && H==0)
      break;

    Point2 p;
    cin >> p.tx >> p.ty;
    cin >> p.kx >> p.ky;

    int d[52][52];
    for(int y=0; y<=H+1; y++){
      for(int x=0; x<=W+1; x++){
	d[y][x] = 1;
      }
    }

    for(int y=1; y<=H; y++){
      for(int x=1; x<=W; x++){
	cin >> d[y][x];
      }
    }

    queue<Point2> que;
    que.push(p);

    map<int, int> n;
    n[mk(p)] = 0;

    while(true){
      if(que.empty()){
	cout << "NA" << endl;
	break;
      }

      p = que.front(); que.pop();

      if(n[mk(p)]>=100){
	cout << "NA" << endl;
	break;
      }

      if(p.tx==p.kx && p.ty==p.ky){
	cout << n[mk(p)] << endl;
	break;
      }

      Point2 q;

      //東
      q = p;
      if(d[q.ty][q.tx+1]==0){
	q.tx = q.tx+1;
      }
      if(d[q.ky][q.kx-1]==0){
	q.kx = q.kx-1;
      }
      if(n.find(mk(q))==n.end()){
	que.push(q);
	n[mk(q)] = n[mk(p)]+1;
      }

      //西
      q = p;
      if(d[q.ty][q.tx-1]==0){
	q.tx = q.tx-1;
      }
      if(d[q.ky][q.kx+1]==0){
	q.kx = q.kx+1;
      }
      if(n.find(mk(q))==n.end()){
	que.push(q);
	n[mk(q)] = n[mk(p)]+1;
      }

      //南
      q = p;
      if(d[q.ty+1][q.tx]==0){
	q.ty = q.ty+1;
      }
      if(d[q.ky-1][q.kx]==0){
	q.ky = q.ky-1;
      }
      if(n.find(mk(q))==n.end()){
	que.push(q);
	n[mk(q)] = n[mk(p)]+1;
      }

      //北
      q = p;
      if(d[q.ty-1][q.tx]==0){
	q.ty = q.ty-1;
      }
      if(d[q.ky+1][q.kx]==0){
	q.ky = q.ky+1;
      }
      if(n.find(mk(q))==n.end()){
	que.push(q);
	n[mk(q)] = n[mk(p)]+1;
      }
    }
  }

  return 0;
}