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 || H > H;
}
int main(){
  char F[52][52];
  int D[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++){
        D[y][x] = INF;
        int a;
        cin >> a;
        F[y][x] = a;
      }
    }


    p.set(tx,ty,kx,ky);
    qa.push(p);
    D[p.ty][p.tx] = 0;
    while(1){
      if(qa.empty()){
        cout << "NA" << endl;
        break;
      }
      p = qa.front();
      qa.pop();
      if(D[p.ty][p.tx] >= 100){
        cout << "NA" << endl;
        break;
      }
      if(p.tx == p.kx && p.ty == p.ky){
        cout << D[p.ty][p.tx] << endl;
        break;
      }

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

    }

  }
  return 0;
}

C++: #include<stdio.h>
#include<iostream>
#include<queue>
#include<string.h>
using namespace std;
struct Y{
int hx,hy,rx,ry,tim;
};
int mp[52][52],c[51][51][51][51];
int main(){
int n,w,h,i,j,a[2]={1,-1},b[2];
Y e;
while(1){
queue<Y> q;
	cin>>w>>h;
	if(w==0&&h==0)break;
	cin>>e.hx>>e.hy>>e.rx>>e.ry;
	e.tim=0;
	q.push(e);
	memset(mp,0,sizeof(mp));
	memset(c,0,sizeof(c));
	for(i=0;i<=h+1;i++){
		mp[i][0]=1;
		mp[i][w+1]=1;
	}
	for(i=0;i<=w+1;i++){
		mp[0][i]=1;
		mp[h+1][i]=1;
	}
	for(i=1;i<=h;i++){
		for(j=1;j<=w;j++){
			cin>>mp[j][i];
		}
	}
	while(!q.empty()){
		e=q.front();
		q.pop();
		if(e.tim>=100||e.hx==e.rx&&e.hy==e.ry)break;
		e.tim++;
		for(i=0;i<2;i++){
			if(mp[e.hy+a[i]][e.hx]!=1&&c[e.hy+a[i]][e.hx][e.ry-a[i]][e.rx]==0&&mp[e.ry-a[i]][e.rx]!=1||mp[e.ry-a[i]][e.rx]!=1&&c[e.hy][e.hx][e.ry-a[i]][e.rx]==0&&mp[e.hy+a[i]][e.hx]==1||mp[e.hy+a[i]][e.hx]!=1&&mp[e.ry-a[i]][e.rx]==1&&c[e.hy+a[i]][e.hx][e.ry][e.rx]==0){
				b[0]=0;																										
				b[1]=0;																																		
				if(mp[e.hy+a[i]][e.hx]!=1){																											
					e.hy+=a[i];																																			
					b[0]=1;																																					
				}																																													
				if(mp[e.ry-a[i]][e.rx]!=1){																																										
					e.ry-=a[i];																																		
					b[1]=1;																																																														
				}		
				c[e.hy][e.hx][e.ry][e.rx]=1;																																																																																																																
				q.push(e);																											
				if(b[0]==1)e.hy-=a[i];																														
				if(b[1]==1)e.ry+=a[i];																											
			}																																																												
			if(mp[e.hy][e.hx+a[i]]!=1&&mp[e.ry][e.rx-a[i]]!=1&&c[e.hy][e.hx+a[i]][e.ry][e.rx-a[i]]==0||mp[e.hy][e.hx+a[i]]!=1&&c[e.hy][e.hx+a[i]][e.ry][e.rx]==0&&mp[e.ry][e.rx-a[i]]==1||mp[e.ry][e.rx-a[i]]!=1&&mp[e.hy][e.hx+a[i]]==1&&c[e.hy][e.hx][e.ry][e.rx-a[i]]==0){
				b[0]=0;
				b[1]=0;
				if(mp[e.hy][e.hx+a[i]]!=1){
					e.hx+=a[i];
					b[0]=1;
				}
				if(mp[e.ry][e.rx-a[i]]!=1){
					e.rx-=a[i];
					b[1]=1;
				}
				c[e.hy][e.hx][e.ry][e.rx]=1;
				q.push(e);
				if(b[0]==1)e.hx-=a[i];
				if(b[1]==1)e.rx+=a[i];
			}
		}
		e.tim--;
	}
	if(e.hy==e.ry&&e.hx==e.rx)cout<<e.tim<<endl;
	else printf("NA\n");
}
return 0;
}