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 := 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 <iostream>
#include <cstring>
#include <queue>
#include <map>
#include <algorithm>
#define fr first
#define sc second
#define INF (2 << 28)
using namespace std;

typedef pair<int, int> iP;
typedef pair<iP, iP> iiP;
typedef pair<iiP, int> iiiP;

int w, h;
iP ts, ks;
int mas[51][51], used[51][51][51][51];
int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};

int bfs(){
  
  fill_n(***used, 51*51*51*51, INF);
  queue <iiiP> que;
  que.push(iiiP(iiP(ts, ks), 0)); used[ts.fr][ts.sc][ks.fr][ks.sc] = 0;
  while(!que.empty()){
    iiiP p = que.front(); que.pop();
    if(p.fr.fr == p.fr.sc){
      if(p.sc >= 100) return -1;
      else return p.sc;
    }
    
    int tx = p.fr.fr.fr, ty = p.fr.fr.sc, kx = p.fr.sc.fr, ky = p.fr.sc.sc;
    if(used[tx][ty][kx][ky] == INF) continue;
    for(int i = 0; i < 4; i++){
      int ntx = tx + dx[i], nty = ty + dy[i];
      int nkx = kx - dx[i], nky = ky - dy[i];
      
      if(mas[nty][ntx] == 1 || !(ntx >= 0 && ntx < w && nty >= 0 && nty < h)) ntx = tx, nty = ty;
      if(mas[nky][nkx] == 1 || !(nkx >= 0 && nkx < w && nky >= 0 && nky < h)) nkx = kx, nky = ky;

      if(used[ntx][nty][nkx][nky] > p.sc + 1){
	que.push(iiiP(iiP(iP(ntx, nty), iP(nkx, nky)), p.sc + 1));
	used[ntx][nty][nkx][nky] = p.sc + 1;
      }
    }
  }
  return -1;

}  

int main(){
  
  while(cin >> w >> h, w||h){
    cin >> ts.fr >> ts.sc;
    cin >> ks.fr >> ks.sc;
    ts.fr--, ts.sc--;
    ks.fr--, ks.sc--;
    for(int i = 0; i < h; i++){
      for(int j = 0; j < w; j++) cin >> mas[i][j];
    }

    int ans = bfs();
    if(ans == -1) cout << "NA" << endl;
    else cout << ans << endl;
  }

}

C++: #include <iostream>
#include <queue>
#include <map>

#define INF 100000000
#define MAX_X 1000
#define MAX_Y 1000

using namespace std;

typedef pair<pair<int,int>,pair<int,int> > P;

int d[MAX_Y][MAX_X][MAX_Y][MAX_X];

int tx,ty,kx,ky,ntx,nty,nkx,nky;
int ans;

short maze[MAX_Y][MAX_X];
int Y,X;

int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};

bool bfs(){
	queue<P> que;
	map<P,int> mat;
	que.push(make_pair(make_pair(ty,tx),make_pair(ky,kx)));
	
	mat[que.front()]=0;
	while (que.size()&&100>=d[nty][ntx][nky][nkx]) {
		P p=que.front();
		que.pop();
		if (p.first.first==p.second.first&&p.first.second==p.second.second) {
			ans=d[p.first.first][p.first.second][p.second.first][p.second.second];
			return true;
		}
		if (mat[que.front()]) {
			continue;
		}

		
		for (int i=0; i<4; i++) {
			ntx=p.first.second+dx[i],nty=p.first.first+dy[i],nkx=p.second.second+dx[i]*(-1),nky=p.second.first+dy[i]*(-1);
			int flag=2;
			if (!(0<=ntx&&ntx<X&&0<=nty&&nty<Y&&maze[nty][ntx]!=1)){
				flag-=1;
				ntx=p.first.second;
				nty=p.first.first;
			}
			if (!(0<=nkx&&nkx<X&&0<=nky&&nky<Y&&maze[nky][nkx]!=1)) {
				flag-=1;
				nkx=p.second.second;
				nky=p.second.first;
			}
			if (flag!=0) {
				que.push(P(make_pair(nty,ntx),make_pair(nky,nkx)));
				d[nty][ntx][nky][nkx]=d[p.first.first][p.first.second][p.second.first][p.second.second]+1;
			}
			mat[que.front()] = d[nty][ntx][nky][nkx];
		}
	}
	return false;
}

int main(){
	while (cin>>X>>Y&&X&&Y) {
		cin>>tx>>ty>>kx>>ky;
		tx-=1;
		ty-=1;
		kx-=1;
		ky-=1;
		for (int i=0; i<Y; i++) {
			for (int j=0; j<X; j++) {
				cin>>maze[i][j];
			}
		}
		if(bfs()){
			cout << ans <<endl;
		}
		else {
			cout << "NA" << endl;
		}
	}
}