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 := &Status{}
		*now = *pq[0]
		pq = pq[1:]
		if ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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 <iostream>
#include <queue>
using namespace std;

const int INF = 100000000;

class Twin{
public:

  int tx;
  int ty;
  int kx;
  int ky;
  int n;
};

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

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

    int tx, ty;
    int kx, ky;
    cin >> tx >> ty;
    cin >> kx >> ky;

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

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

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

    queue<Twin> que;

    Twin p;
    p.tx = tx;  p.ty = ty;
    p.kx = kx;  p.ky = ky;
    p.n = 0;
    que.push(p);

    D[p.ty][p.tx] = 0;
    D[p.ky][p.kx] = 0;

    while(!que.empty()){
      p = que.front(); que.pop();

      //cout << D[p.ty][p.tx] << ' ' << p.tx << ',' << p.ty << endl;
      //cout << " ," << p.kx << ',' << p.ky << endl;

      if(p.tx==p.kx && p.ty==p.ky){
	/*for(int y=1; y<=H; y++){
	  for(int x=1; x<=W; x++){
	    cout << D[y][x] << ' ';
	  }
	  cout << endl;
	  }*/
	cout << p.n << endl;
	break;
      }
      if(p.n>=100){
	//cout << p.n << endl;
	cout << "NA" << endl;
	break;
      }

      if(F[p.ty-1][p.tx]==0 || F[p.ky+1][p.kx]==0){//T上
	if(D[p.ty-1][p.tx]>=D[p.ty][p.tx]/* && D[p.ky+1][p.kx]>=D[p.ky][p.kx]*/){
	  //cout << "T-top" << endl;
	  Twin q;
	  if(F[p.ty-1][p.tx]==0){
	    q.tx = p.tx;  q.ty = p.ty-1;
	    if(D[q.ty][q.tx]>D[p.ty][p.tx]){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	  }
	  else{
	    q.tx = p.tx;  q.ty = p.ty;
	    if(D[q.ty][q.tx]>D[p.ty][p.tx]){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	    else if(q.tx==p.tx && q.ty==p.ty){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	  }
	  if(F[p.ky+1][p.kx]==0){
	    q.kx = p.kx;  q.ky = p.ky+1;
	    //D[q.ky][q.kx] = 0;
	  }
	  else{
	    q.kx = p.kx;  q.ky = p.ky;
	    //D[q.ky][q.kx] = 0;
	  }
	  q.n = p.n+1;
	  //cout << q.ty << ' ' <<  q.ky << endl;
	  que.push(q);
	}
      }
      if(F[p.ty+1][p.tx]==0 || F[p.ky-1][p.kx]==0){//T下
	if(D[p.ty+1][p.tx]>=D[p.ty][p.tx]/* && D[p.ky-1][p.kx]>=D[p.ky][p.kx]*/){
	  //cout << "T-bottom" << endl;
	  Twin q;
	  if(F[p.ty+1][p.tx]==0){
	    q.tx = p.tx;  q.ty = p.ty+1;
	    if(D[q.ty][q.tx]>D[p.ty][p.tx]){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	  }
	  else{
	    q.tx = p.tx;  q.ty = p.ty;
	    if(D[q.ty][q.tx]>D[p.ty][p.tx]){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	    else if(q.tx==p.tx && q.ty==p.ty){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	  }
	  if(F[p.ky-1][p.kx]==0){
	    q.kx = p.kx;  q.ky = p.ky-1;
	    //D[q.ky][q.kx] = 0;
	  }
	  else{
	    q.kx = p.kx;  q.ky = p.ky;
	    //D[q.ky][q.kx] = 0;
	  }
	  q.n = p.n+1;
	  //cout << q.ty << ' ' <<  q.ky << endl;
	  que.push(q);
	}
      }
      if(F[p.ty][p.tx-1]==0 || F[p.ky][p.kx+1]==0){//T左
	if(D[p.ty][p.tx-1]>=D[p.ty][p.tx]/* && D[p.ky][p.kx+1]>=D[p.ky][p.kx]*/){
	  //cout << "T-left" << endl;
	  Twin q;
	  if(F[p.ty][p.tx-1]==0){
	    q.tx = p.tx-1;  q.ty = p.ty;
	    if(D[q.ty][q.tx]>D[p.ty][p.tx]){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	  }
	  else{
	    q.tx = p.tx;  q.ty = p.ty;
	    if(D[q.ty][q.tx]>D[p.ty][p.tx]){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	    else if(q.tx==p.tx && q.ty==p.ty){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	  }
	  if(F[p.ky][p.kx+1]==0){
	    q.kx = p.kx+1;  q.ky = p.ky;
	    //D[q.ky][q.kx] = 0;
	  }
	  else{
	    q.kx = p.kx;  q.ky = p.ky;
	    //D[q.ky][q.kx] = 0;
	  }
	  q.n = p.n+1;
	  //cout << q.tx << ' ' <<  q.kx << endl;
	  que.push(q);
	}
      }
      if(F[p.ty][p.tx+1]==0 || F[p.ky][p.kx-1]==0){//T右
	if(D[p.ty][p.tx+1]>=D[p.ty][p.tx]/* && D[p.ky][p.kx-1]>=D[p.ky][p.kx]*/){
	  //cout << "T-right" << endl;
	  Twin q;
	  if(F[p.ty][p.tx+1]==0){
	    q.tx = p.tx+1;  q.ty = p.ty;
	    if(D[q.ty][q.tx]>D[p.ty][p.tx]){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	  }
	  else{
	    q.tx = p.tx;  q.ty = p.ty;
	    if(D[q.ty][q.tx]>D[p.ty][p.tx]){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	    else if(q.tx==p.tx && q.ty==p.ty){
	      D[q.ty][q.tx] = D[p.ty][p.tx]+1;
	    }
	  }
	  if(F[p.ky][p.kx-1]==0){
	    q.kx = p.kx-1;  q.ky = p.ky;
	    //D[q.ky][q.kx] = 0;
	  }
	  else{
	    q.kx = p.kx;  q.ky = p.ky;
	    //D[q.ky][q.kx] = 0;
	  }
	  q.n = p.n+1;
	  //cout << q.tx << ' ' <<  q.kx << endl;
	  que.push(q);
	}
      }
    }

    if(p.tx==p.kx && p.ty==p.ky){
      continue;
    }
    else if(p.n<100){
      cout << "NA" << endl;
    }
  }

  return 0;
}