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 = 1000000;
int H,W;
class Point{
public:
  int tx;
  int ty;
  int kx;
  int ky;
  void set(int a,int b,int c,int d){
    tx = a;
    ty = b;
    kx = c;
    ky = d;
  }
};

int is_out_of_area(int y,int x){
  return x < 1 || x > W || y < 1 || y > H;
}
int main(){
  char F[52][52];
  int D[52][52][52][52];
  queue<Point> qa;
  Point p;
  int tx,ty,kx,ky;
  while(1){
    cin >> W >> H;
    if(W == 0 && H == 0)
    break;
    cin >> tx >> ty >> kx >> ky;

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


    p.set(tx,ty,kx,ky);
    qa.push(p);
    D[p.ty][p.tx][p.ky][p.kx] = 0;
    while(1){
      if(qa.empty()){
        cout << "NA" << endl;
        break;
      }
      p = qa.front();
      qa.pop();
      if(D[p.ty][p.tx][p.ky][p.kx] >= 99){
        cout << "NA" << endl;
        break;
      }
      if(p.tx == p.kx && p.ty == p.ky){
        cout << D[p.ty][p.tx][p.ky][p.kx] << endl;
        break;
      }

      if(D[p.ty-1][p.tx][p.ky+1][p.kx] == INF){
          int inc_ty = -1 , inc_ky = 1;
          if(is_out_of_area(p.ty-1,p.tx) || F[p.ty-1][p.tx]){
            inc_ty = 0;
          } else if(is_out_of_area(p.ky+1,p.kx) || F[p.ky+1][p.kx]){
            inc_ky = 0;
          }

          Point q;
          q.set(p.tx,p.ty + inc_ty,p.kx,p.ky+inc_ky);
          if(inc_ty  || inc_ky){
            qa.push(q);
          }
          D[p.ty-1][p.tx][p.ky+1][p.kx] = D[p.ty][p.tx][p.ky][p.kx] + 1;
      }

      if(D[p.ty+1][p.tx][p.ky-1][p.kx] == INF){
          int inc_ty = -1 , inc_ky = 1;
          if(is_out_of_area(p.ty+1,p.tx) || F[p.ty+1][p.tx]){
            inc_ty = 0;
          } else if(is_out_of_area(p.ky-1,p.kx) || F[p.ky-1][p.kx]){
            inc_ky = 0;
          }

          Point q;
          q.set(p.tx,p.ty + inc_ty,p.kx,p.ky+inc_ky);
          if(inc_ty  || inc_ky){
            qa.push(q);
          }
          D[p.ty+1][p.tx][p.ky-1][p.kx] = D[p.ty][p.tx][p.ky][p.kx] + 1;
      }

      if(D[p.ty][p.tx-1][p.ky][p.kx+1] == INF){
          int inc_tx = -1 , inc_kx = 1;
          if(is_out_of_area(p.ty,p.tx + inc_tx) || F[p.ty][p.tx + inc_tx]){
            inc_tx = 0;
          } else if(is_out_of_area(p.ky,p.kx + inc_kx) || F[p.ky][p.kx + inc_kx]){
            inc_kx = 0;
          }

          Point q;
          q.set(p.tx + inc_tx,p.ty,p.kx + inc_kx,p.ky);
          if(inc_tx  | inc_kx){
            qa.push(q);
          }
          D[p.ty][p.tx-1][p.ky][p.kx+1] = D[p.ty][p.tx][p.ky][p.kx] + 1;
      }
      if(D[p.ty][p.tx+1][p.ky][p.kx-1] == INF){
          int inc_tx = 1 , inc_kx = -1;
          if(is_out_of_area(p.ty,p.tx + inc_tx) || F[p.ty][p.tx + inc_tx]){
            inc_tx = 0;
          } else if(is_out_of_area(p.ky,p.kx + inc_kx) || F[p.ky][p.kx + inc_kx]){
            inc_kx = 0;
          }

          Point q;
          q.set(p.tx + inc_tx,p.ty,p.kx + inc_kx,p.ky);
          if(inc_tx  | inc_kx){
            qa.push(q);
          }
          D[p.ty][p.tx+1][p.ky][p.kx-1] = D[p.ty][p.tx][p.ky][p.kx] + 1;
      }

    }



  }
  return 0;
}

C++: #include<cstdio>
#include<string.h>

using namespace std;

#define MAX 51

int xy[MAX][MAX];
int cost[MAX][MAX][MAX][MAX];
int X,Y;

int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};

struct state{
  int tx;
  int ty;
  int kx;
  int ky;
  int co;
  state(){}
  state(int tx,int ty,int kx,int ky,int co):
    tx(tx),ty(ty),kx(kx),ky(ky),co(co){}
};

int solve(int tx,int ty,int kx,int ky){

  memset(cost,101,sizeof(cost));

  queue<state> q;
  q.push( state(tx,ty,kx,ky,0) );

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

    if(p.co==100){
      break;
    }

    tx=p.tx;
    ty=p.ty;
    kx=p.kx;
    ky=p.ky;

    for(int i=0;i<4;i++){
      
      if(kx+dx[i]*-1 < 0 || ky+dy[i]*-1 <0 || kx+dx[i]*-1 >= X || ty+dy[i]*-1 >= Y || 
	 tx+dx[i] < 0 || ty+dy[i] <0 || tx+dx[i] >= X || ty+dy[i] >= Y )
	continue;

      cost[tx][ty][kx][ky]=p.co;

      if( cost[tx+dx[i]][ty+dy[i]][kx+dx[i]*-1][ky+dy[i]*-1] < p.co)
	continue;

      if( xy[ty+dy[i]][tx+dx[i]]==1 || xy[ky+dy[i]*-1][kx+dx[i]*-1]==1 )
	continue;
      
      if(tx+dx[i] == kx+dx[i]*-1 && ty+dy[i] == ky+dy[i]*-1)
	return p.co+1;

      q.push( state(tx+dx[i],ty+dy[i],kx+dx[i]*-1,ky+dy[i]*-1,p.co+1) );

    }
  }
  return -1;
} 

main(){
  
  int i,j;
  int kx,ky,tx,ty;
  int n;

  while(1){
    
    cin >> X >> Y;

    if(X==0 && Y==0) break;
    
    cin >> tx >> ty;
    cin >> kx >> ky;
    
    for(i=0;i<Y;i++){
      for(j=0;j<X;j++){
	cin >> xy[i][j];
      }
    }
    
    n=solve(tx-1,ty-1,kx-1,ky-1);
    
    if(n==-1)
      cout << "NA" << endl;
    else
      cout << n << endl;
  }
  return 0;
}