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 unsigned char INF = 255;
int H,W;
class Point{
public:
  int tx;
  int ty;
  int kx;
  int ky;
  int d;
  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(){
  bool F[52][52];
  bool 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] = 1;
          }
        }
      }
    }
    while(!qa.empty()){
      qa.pop();
    }
    p.set(tx,ty,kx,ky);
    qa.push(p);
    D[p.ty][p.tx][p.ky][p.kx] = 0;
    int counter=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] >= 100){
        cout << "NA" << endl;
        break;
      }
      if(p.tx == p.kx && p.ty == p.ky){
        cout << p.d << endl;
        break;
      }
      counter++;
      if(D[p.ty-1][p.tx][p.ky+1][p.kx]){

          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;
          }
          if(is_out_of_area(p.ky+1,p.kx) || F[p.ky+1][p.kx]){
            inc_ky = 0;
          }

          if(inc_ty || inc_ky){
            Point q;
            q.set(p.tx,p.ty + inc_ty,p.kx,p.ky+inc_ky);
            q.d = p.d + 1;
            qa.push(q);
            D[p.ty + inc_ty][p.tx][p.ky + inc_ky][p.kx] = 0;
          }
      }

      if(D[p.ty+1][p.tx][p.ky-1][p.kx]){

          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;
          }
          if(is_out_of_area(p.ky-1,p.kx) || F[p.ky-1][p.kx]){
            inc_ky = 0;
          }

          if(inc_ty || inc_ky){
            Point q;
            q.set(p.tx,p.ty + inc_ty,p.kx,p.ky+inc_ky);
            q.d = p.d + 1;
            qa.push(q);
            D[p.ty + inc_ty][p.tx][p.ky + inc_ky][p.kx] = 0;
          }
      }

      if(D[p.ty][p.tx-1][p.ky][p.kx+1]){

          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;
          }
          if(is_out_of_area(p.ky,p.kx + inc_kx) || F[p.ky][p.kx + inc_kx]){
            inc_kx = 0;
          }

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

          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;
          }
          if(is_out_of_area(p.ky,p.kx + inc_kx) || F[p.ky][p.kx + inc_kx]){
            inc_kx = 0;
          }

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

    }
  }
  return 0;
}

C++: #include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<complex>
#include<cmath>
#include<algorithm>
#include<map>
#include<vector>
#include<sstream>
#include<queue>
#include<iostream>
using namespace std;
struct data{
    int x;
    int y;
    int u;
    int v;
    int t;
};

bool vis[60][60][60][60] = {};
const int dx[] = {1,0,-1,0},dy[] = {0,1,0,-1};
int main(void){
    int w,h;
    while(cin>>w>>h,w){
        int x,y,u,v;
        cin>>x>>y>>u>>v;
        bool screen[60][60] = {};
        for(int i = 0;i < h;i++){
            for(int j = 0;j < w;j++){
                cin>>screen[i][j];
            }
        }
        data D;
        D.x = x,D.y = y;
        D.u = u,D.v = v;
        D.t = 0;
        queue<data> Q;
        Q.push(D);

        while(!Q.empty()){
            data E = Q.front();Q.pop();

            if(E.x == E.u&&E.y == E.v){
                cout<<E.t<<endl;
                goto e;
            }
            if(E.t>99)break;
            for(int i = 0;i < 4;i++){

                    data F = E;
                    F.t++;
                    F.x+=dx[i],F.y+=dy[i],F.u+=dx[(i+2)%4],F.v+=dy[(i+2)%4];
                    if(!(0<=F.x&&F.x<w&&0<=F.y&&F.y<h)){
                        F.x = E.x,F.y = E.y;
                    }
                    else if(screen[F.x][F.y])F.x = E.x,F.y = E.y;
                    if(!(0<=F.u&&F.u<w&&0<=F.v&&F.v<h)){
                        F.u = E.u,F.v = E.v;
                    }
                    else if(screen[F.u][F.v])F.u = E.u,F.v = E.v;
                    if(!vis[F.x][F.y][F.u][F.v]&&!vis[F.u][F.v][F.x][F.y]){

                        vis[F.x][F.y][F.u][F.v] = true;
                        vis[F.u][F.v][F.x][F.y] = true;
                        Q.push(F);
                    }

            }

        }
        cout<<"NA"<<endl;
        e:;
    }


    return 0;
}