Go: package main

import (
	"container/heap"
	"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 (pq PQStatus) Len() int {
	return len(pq)
}
func (pq PQStatus) Less(i, j int) bool {
	if pq[i].Turn == pq[j].Turn {
		return pq[i].Person.Distance() < pq[j].Person.Distance()
	}
	return pq[i].Turn < pq[j].Turn
}

func (pq PQStatus) Swap(i, j int) {
	pq[i], pq[j] = pq[j], pq[i]
}

func (pq *PQStatus) Push(x interface{}) {
	item := x.(*Status)
	*pq = append(*pq, item)
}

func (pq *PQStatus) Pop() interface{} {
	old := *pq
	n := len(old)
	item := old[n-1]
	*pq = old[0 : n-1]
	return item
}

func solve(h, w int64) {
	var tx, ty, kx, ky int64
	fmt.Scan(&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)
	heap.Init(&pq)
	heap.Push(&pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		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 += 1
			if next.Turn < 100 {
				heap.Push(&pq, next)
			}
		}
	}
	fmt.Println("NA")
}

func main() {
	var h, w int64
	for {
		fmt.Scan(&h, &w)
		if h == 0 && w == 0 {
			break
		}
		solve(h, w)
	}
}

C++: #include <iostream>
#include <cstdio>
#include <cstdlib>
#include <math.h>
#include <vector>
#include <queue>
#include <algorithm>
#include <sstream>
#include <string>
using namespace std;
#define FOR(I,N) for(int I = 0; I < (int)(N); I++)
#define FIN(V) cout<<V<<endl
#define pb push_back
#define INF (1 << 30)
typedef pair<int, int> P;

int solve();
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
int w, h, tx, ty, kx, ky;
int maps[51][51];
int memo[51][51][51][51];


struct Data{
    P pt, pk;
    int cnt;
    Data(P pt_, P pk_, int cnt_){
        pt = pt_;
        pk = pk_;
        cnt = cnt_;
    }
    Data(){}
};

int main(void){
    while(cin >> w >> h, w){
        cin >> tx >> ty;
        cin >> kx >> ky;
        fill_n(*maps, 51*51, 1);
        FOR(i, h)FOR(j, w){
            cin >> maps[i+1][j+1];
        }
        int a = solve();
        if(a == -1 || a >= 100){FIN("NA");continue;}
        else FIN(a);
    }
    return 0;    
}


int solve(){
    int ans = -1;
    fill_n(***memo, 51*51*51*51, INF);
    queue<Data> que;
    que.push(Data(P(tx,ty), P(kx, ky), 0));
    while(que.size()){
        Data data = que.front();
        que.pop();
        int x1 = data.pt.first;
        int y1 = data.pt.second;
        int x2 = data.pk.first;
        int y2 = data.pk.second;
        int cost = data.cnt;
        if(cost > 100)break;
        if(memo[x1][y1][x2][y2] <= cost)continue;
        memo[x1][y1][x2][y2] = cost;
        if(x1 == x2 && y1 == y2){ans = cost;break;};
        FOR(i, 4){
            int nx1 = x1 + dx[i];
            int ny1 = y1 + dy[i];
            int nx2 = x2 - dx[i];
            int ny2 = y2 - dy[i];
            if(maps[ny1][nx1] == 1){nx1 = x1;ny1 = y1;};
            if(maps[ny2][nx2] == 1){nx2 = x2;ny2 = y2;};
            que.push(Data(P(nx1,ny1), P(nx2, ny2), cost+1));
        }
    }

    return ans;
}

C++: #include<iostream>
#include<queue>
#include<cstdio>
#include<cstring>

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( 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;

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


      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;
}

C++: #include<iostream>
#include<queue>
#include<map>
using namespace std;
const int INF=(1<<21);
typedef pair<int,int> P;
int x,y;
int tx,ty;
int kx,ky;
int t_check[50][50];
int k_check[50][50];
int depart[50][50];
int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int ans=0;

int bfs(){
  queue<P> t_que;
  queue<P> k_que;

  for(int i=0;i<y;i++){
    for(int j=0;j<x;j++){
      t_check[i][j]=k_check[i][j]=INF;
    }
  }

  t_check[ty][tx]=0;
  k_check[ky][kx]=0;

  t_que.push(P(ty,tx));
  k_que.push(P(ky,kx));

  while(t_que.size()){
    P tp=t_que.front();t_que.pop();
    P kp=k_que.front();k_que.pop();
    if(tp.first==kp.first && tp.second==kp.second){
      return t_check[tp.first][tp.second];
    }

    for(int i=0;i<4;i++){
      int tnx=tp.second+dx[i];
      int tny=tp.first+dy[i];
      int knx=kp.second-(dx[i]);
      int kny=kp.first-(dy[i]);

      if(0<=tnx && tnx<x && 0<=tny && tny<y && depart[tny][tnx]!=1 && t_check[tny][tnx]==INF  &&  0<=knx && knx<x && 0<=kny && kny<y && depart[kny][knx]!=1 && k_check[kny][knx]==INF){

	t_que.push(P(tny,tnx));
	k_que.push(P(kny,knx));
	t_check[tny][tnx]=t_check[tp.first][tp.second]+1;
	k_check[kny][knx]=k_check[kp.first][kp.second]+1;

      }
    }
    if(!t_que.size()){
      return 0;
    }
  }
}
int main(){
  while(1){
    cin>> x>> y;
  if(x==0 && y==0){
    break;
  }
  cin>> tx>> ty;
  cin>> kx>> ky;
  for(int i=0;i<y;i++){
    for(int j=0;j<x;j++){
      cin>> depart[i][j];
    }
  }
  ans=bfs();
  if(ans==0){
    cout<< "NA"<<endl;
  }else{
    cout<< ans<< endl;
  }
  }
}