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 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++
			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 <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
using namespace std;

#define N 50

static int d[ N ][ N ];
static int x, y;

struct P
{
  int tx; int ty;
  int kx; int ky;
  int t;
  P move ( int dtx, int dty, int dkx, int dky )
  {
    P res = { tx + dtx, ty + dty, kx + dkx, ky + dky, t + 1 };

    if ( res.tx < 0 || res.tx >= x || res.ty < 0 || res.ty >= y
      || d[ res.tx ][ res.ty ] ) { res.tx -= dtx; res.ty -= dty; }
    if ( res.kx < 0 || res.kx >= x || res.ky < 0 || res.ky >= y
      || d[ res.kx ][ res.ky ] ) { res.kx -= dkx; res.ky -= dky; }

    return ( res );
  }
};

static int t[ N ][ N ][ N ][ N ];

int
main (
  int   argc,
  char *argv[ ]
  )
{
  int i, j;

  for ( ; ; )
  {
    queue<P> lis;
    P p;

    scanf ( "%d%d", &x, &y );
    if ( x == 0 && y == 0 ) break ;
    scanf ( "%d%d%d%d", &p.tx, &p.ty, &p.kx, &p.ky );
    --p.tx; --p.ty; --p.kx; --p.ky;
    for ( j = 0; j < y; ++j )
    for ( i = 0; i < x; ++i )
      scanf ( "%d", &d[ i ][ j ] );

    p.t = 0;
    lis.push ( p );
    memset ( t, 0, sizeof ( t ) );
    while ( !lis.empty ( ) )
    {
      p = lis.front ( );
      lis.pop ( );

      if ( t[ p.tx ][ p.ty ][ p.kx ][ p.ky ] ) continue ;
      t[ p.tx ][ p.ty ][ p.kx ][ p.ky ] = 1;
      if ( p.tx == p.kx && p.ty == p.ky )
      {
        printf ( "%d\n", p.t );
        goto CONT;
      }

      if ( p.t + 1 < 100 )
      {
        lis.push ( p.move (  1,  0, -1,  0 ) );
        lis.push ( p.move ( -1,  0,  1,  0 ) );
        lis.push ( p.move (  0,  1,  0, -1 ) );
        lis.push ( p.move (  0, -1,  0,  1 ) );
      }
    }
    puts ( "NA" );
CONT: ;
  }

  return ( EXIT_SUCCESS );
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int h,w;
int map[100][100];
int qtx[300000],qty[300000],qkx[300000],qky[300000];
int ql[300000];
int tail,head;
int ans;
int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};
bool vis[60][60][60][60];
bool bend;
void BFS(int tx,int ty,int kx,int ky,int len){
	if(len==100)return;
	if(tx==kx&&ty==ky){
		ans=len;
		bend=true;
		return;
	}
	for(int i=0;i<4;i++){
		bool mt=false,mk=false;
		if(tx+dx[i]>=0&&tx+dx[i]<w&&ty+dy[i]>=0&&ty+dy[i]<h){
			if(map[ty+dy[i]][tx+dx[i]]==0){
				mt=true;
			}
		}
		if(kx-dx[i]>=0&&kx-dx[i]<w&&ky-dy[i]>=0&&ky-dy[i]<h){
			if(map[ky-dy[i]][kx-dx[i]]==0){
				mk=true;
			}
		}
		qtx[tail]=tx+mt*dx[i],qty[tail]=ty+mt*dy[i];
		qkx[tail]=kx-mk*dx[i],qky[tail]=ky-mk*dy[i];
		ql[tail]=len+1;
		tail++;
	}
}
int main(){
	while(true){
	cin>>w>>h;
	if(w==0&&h==0)break;
	for(int i=0;i<60;i++){
		for(int j=0;j<60;j++){
			for(int k=0;k<60;k++){
				for(int r=0;r<60;r++){
					vis[i][j][k][r]=false;
				}
			}
		}
	}
	int tx,ty,kx,ky;
	cin>>tx>>ty>>kx>>ky;
	tx--,ty--,kx--,ky--;
	for(int i=0;i<h;i++){
		for(int j=0;j<w;j++){
			cin>>map[i][j];
		}
	}
	ans=869121;
	qtx[0]=tx,qty[0]=ty,qkx[0]=kx,qky[0]=ky;
	ql[0]=0;
	tail=1,head=0;
	bend=false;
	while(true){
		if(tail==head)break;
		if(!vis[qtx[head]][qty[head]][qkx[head]][qky[head]]){
		vis[qtx[head]][qty[head]][qkx[head]][qky[head]]=true;
		BFS(qtx[head],qty[head],qkx[head],qky[head],ql[head]);
		}
		if(bend)break;
		head++;
	}
	if(ans==869121)cout<<"NA"<<endl;
	else cout<<ans<<endl;
	}
	return 0;
}