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>
#include<map>
#include<cstring>
using namespace std;

struct node 
{
  int step;
  int tx,ty;
  int kx,ky;
  node(int s,int ttx,int tty,int kkx,int kky):
    step(s),tx(ttx),ty(tty),kx(kkx),ky(kky){} 
};
  
int main()
{
  int x,y;
  for(;cin>>x>>y,x;)
    {
      bool data[60][60];
      int tx,ty,kx,ky;
      cin>>tx>>ty>>kx>>ky;
      memset(data,false,sizeof(data));
      for(int i=1;i<=x;i++)
	for(int j=1;j<=y;j++)
	  {
	    char tmp;
	    cin>>tmp;
	    data[j][i]=(tmp=='0');
	  }
      queue<node> qu;
      qu.push(node(0,tx,ty,kx,ky));
      map< pair<pair<int,int>,pair<int,int> > ,bool >hash;
      int ans=-1;
      int dx[]={0,0,1,-1};
      int dy[]={1,-1,0,0};
      while(!qu.empty())
	{
	  node tmp=qu.front();
	  qu.pop();
	  //	  cout<<tmp.step<<" "<<tmp.tx<<" "<<tmp.ty<<" "<<tmp.kx<<" "<<tmp.ky<<endl;
	  if(hash[make_pair(make_pair(tmp.tx,tmp.ty),make_pair(tmp.kx,tmp.ky))])
	    continue;
	  if(tmp.tx==tmp.kx && tmp.ty==tmp.ky)
	    {
	      ans=tmp.step;
	      break;
	    }
	  if(tmp.step>=99)
	    continue;
	  hash[make_pair(make_pair(tmp.tx,tmp.ty),make_pair(tmp.kx,tmp.ky))]=true;
	  for(int i=0;i<4;i++)
	    {
	      int ttx=tmp.tx,tty=tmp.ty,tkx=tmp.kx,tky=tmp.ky;
	      if(data[ttx+dx[i]][tty+dy[i]])
		{
		  ttx+=dx[i];
		  tty+=dy[i];
		}
	      if(data[tkx-dx[i]][tky-dy[i]])
		{
		  tkx-=dx[i];
		  tky-=dy[i];
		}
	      //cout<<"make"<<ttx<<" "<<tkx<<" "<<tty<<" "<<tty<<endl;
	      if(!hash[make_pair(make_pair(ttx,tty),make_pair(tkx,tky))])
		qu.push(node(tmp.step+1,ttx,tty,tkx,tky));
	    }
	}
      if(ans==-1)
	cout<<"NA"<<endl;
      else
	cout<<ans<<endl;

    }
}

C++: #include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a) (a).begin(),(a).end()
#define pb emplace_back
#define INF (1e9+1)

//verified AOJ GRL_1
#define MAX_V 2500
struct edge{int to,cost;};


void dijkstra(int s, vector<int> &d, vector<edge> G[MAX_V]){
    queue<pii> que;
    rep( i,d.size() )d[i]=INF;
    d[s] = 0;
    que.push( pii(0,s) );
    
    while( que.size() ){
        pii p=que.front();
        que.pop();
        
        int v=p.second;
        if(d[v]<p.first)continue;
        
        rep(i,G[v].size()){
            edge e=G[v][i];
            if(d[e.to]>d[v]+e.cost){
                d[e.to]=d[v]+e.cost;
                que.push(pii(d[e.to],e.to));
            }
        }
    }
}

int w,h;
int v[51][51];

int f(int ay, int ax, int by, int bx ){
    return (ay*w+ax)*w*h + by*w+bx;
}

int main(){
    while(cin>>w>>h&&(w||h)){
        int ax,ay,bx,by;
        cin>>ax>>ay>>bx>>by;
        ax--,ay--,bx--,by--;
        
        rep(i,h)rep(j,w)cin>>v[i][j];
        
        int dy[]={1,0,-1,0};
        int dx[]={0,1,0,-1};
        
        static vector<edge> G[2500*2500+1];
        rep(i,2500*2500+1)G[i].clear();
        
        rep(ix,w){
            rep(iy,h){
                rep(jx,w){
                    rep(jy,h){
                        if(ix==jx&&iy==jy)continue;
                        rep(k,4){
                            int ddix = ix+dx[k];
                            int ddjx = jx-dx[k];
                            int ddiy = iy+dy[k];
                            int ddjy = jy-dy[k];
                            
                            if(ddiy<0 || ddiy>=h || ddix<0 || ddix>=w || v[ddiy][ddix])ddiy = iy, ddix = ix;
                            if(ddjy<0 || ddjy>=h || ddjx<0 || ddjx>=w || v[ddjy][ddjx])ddjy = jy, ddjx = jx;
                            G[f(ix,iy,jx,jy)].pb(edge{f(ddix, ddiy, ddjx, ddjy),1});
                        }
                    }
                }
            }
        }
        vector<int> d(2500*2500+1);
        dijkstra(f(ax,ay,bx,by),d,G);
        int ans = INF;
        rep(i,h){
            rep(j,w){
                if(v[i][j])continue;
                ans = min(ans,d[f(i,j,i,j)]);
            }
        }
        if(ans>=100)cout<<"NA"<<endl;
        else cout<<ans<<endl;
    }
}