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 (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)
	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)
	//pq.Push(start)
	pq = append(pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]int64, 0)
	ans := int64(101)
	for pq.Len() > 0 {
		//now := heap.Pop(&pq).(*Status)
		//now := pq.Pop().(*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 += 1
			if next.Turn <= 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				pq = append(pq, next)
			}
		}
	}
	if ans == 101 {
		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<complex>
#include<algorithm>
#include<iostream>
#include<iomanip>
#include<cmath>
#include<vector>
#include<map>
#include<sstream>
#include<ctime>
#include<cstdio>
#include<cstdlib>
#include<cassert>
#include<deque>
#include<queue>
#include<climits>
#include<list>
#include<stack>
#include<ctime>
#define all(n) n.begin(),n.end()
#define REP(i,s,n) for(int i=s;i<n;i++)
#define rep(i,n) REP(i,0,n)
#define PPPinsert(a,b,c,d,e,f) PPP(PP(P(a,b),P(c,d)),P(e,f))
#define F first
#define S second
#define pb push_back
#define INF (1<<27)
#define EPS 1e-10
#define equals(a,b) (fabs((a)-(b)) < EPS)

using namespace std;
typedef pair<int,int> P;
typedef pair<P,P> PP;
typedef pair<PP,P> PPP;
typedef unsigned long long ull;
typedef long long ll;
const int dx[4] = {0,1,0,-1};
const int dy[4] = {1,0,-1,0};

int rdir(int i){
  switch(i){
  case 0:
    return 2;
  case 1:
    return 3;
  case 2:
    return 0;
  case 3: 
    return 1;
  default:
    return -1; 
  }
}

class Pox{
private:
  PPP element;
public:

  Pox(){}
  Pox(PPP element):element(element){}

  PPP get(){
    return element;
  }  

  void print(){
    cout << "takayuki " << element.F.F.F << "," << element.F.F.S << " : kazuyuki " << element.F.S.F << " : " << element.F.S.S << " : cost " << element.S.F << " : distance " << element.S.S << endl;   
  }

};

struct Comparator_X{
  bool operator() (Pox &a,Pox &b){
    if(a.get().S.F != a.get().S.F)return a.get().S.F < b.get().S.F;
    return a.get().S.S < b.get().S.S;
  }
};

int main(){
  int h,w;
  while(true)
    {
      cin >> w >> h;
      if(w+h == 0)break;
      P takayuki,kazuyuki;
      cin >> takayuki.F >> takayuki.S;
      cin >> kazuyuki.F >> kazuyuki.S;

      PPP first_element;//PPP(PP(P(takayuki-x,takayuki-y),P(kazuyuki-x,kazuyuki-y)),P(cost,distance))
      first_element = PPPinsert(takayuki.F,takayuki.S,kazuyuki.F,kazuyuki.S,0,abs(takayuki.F-kazuyuki.F)+abs(takayuki.S-kazuyuki.S));


      bool bmap[h][w];
      bool used_t[h][w],used_h[h][w];
      rep(i,h)
	{
	  rep(j,w)
	    {
	      cin >> bmap[i][j];
	      used_t[i][j] = false,used_h[i][j] = false;     
	    }
	}

      used_t[takayuki.S][takayuki.F] = used_h[kazuyuki.S][kazuyuki.F] = true;

      priority_queue<Pox,vector<Pox>,Comparator_X> pq;
      pq.push(first_element);

      bool fin = false;

      while(!pq.empty())
	{
	  Pox pox = pq.top(); pq.pop();
	  
	  for(int i=0;i<4;i++)
	    {
	      int t_nx,t_ny,h_nx,h_ny;
	      t_nx = pox.get().F.F.F + dx[i],t_ny = pox.get().F.F.S + dy[i];
	      h_nx = pox.get().F.S.F + dx[rdir(i)],h_ny = pox.get().F.S.S + dy[rdir(i)];

	      if(used_t[t_ny][t_ny] && used_h[h_ny][h_nx])
		continue;	      

	      if(!(0<= t_nx && t_nx < w && 0<= t_ny && t_ny < h) || bmap[t_ny][t_nx])
		continue;

	      if(!(0<= h_nx && h_nx < w && 0<= h_ny && h_ny < h) || bmap[h_ny][h_nx])
		continue;

	      if(t_nx == h_nx && t_ny == h_ny)
		{
		  cout << pox.get().S.F+1 << endl;
		  fin = true;
		  break;
		}

	      used_h[h_ny][h_nx] = used_t[t_ny][t_nx] = true;
	      Pox inpox = Pox(PPPinsert(t_nx,t_ny,h_nx,h_ny,pox.get().S.F+1,abs(t_nx-h_nx)+abs(t_ny-h_ny)));
	      pq.push(inpox);
	    }

	}      

      if(!fin)
        cout << "NA" << endl;
	

      
    }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;

const int INF = 1 << 30;
int dy[] = {-1, 0, 1, 0};
int dx[] = {0, -1, 0, 1};
int W, H;
int tx, ty;
int kx, ky;
int d[50][50];
int dist[50][50][50][50];

int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  
  while (cin >> W >> H, W) {
    cin >> tx >> ty >> kx >> ky;
    tx--, ty--, kx--, ky--;
    for (int i = 0; i < H; i++) {
      for (int j = 0; j < W; j++) {
        cin >> d[i][j];
      }
    }
    fill_n((int*)dist, 50 * 50 * 50 * 50, INF);
    dist[ty][tx][ky][kx] = 0;
    using P = tuple<int, int, int, int>;
    queue<P> que;
    que.emplace(ty, tx, ky, kx);
    bool na = true;
    while (!que.empty()) {
      int ay, ax, by, bx;
      tie(ay, ax, by, bx) = que.front(); que.pop();
      if (dist[ay][ax][by][bx] >= 100) break;
      if (pii(ay, ax) == pii(by, bx)) {
        cout << dist[ay][ax][by][bx] << endl;
        na = false;
        break;
      }
      for (int i = 0; i < 4; i++) {
        int any = ay + dy[i];
        int anx = ax + dx[i];
        int bny = by + dy[(i + 2) % 4];
        int bnx = bx + dx[(i + 2) % 4];
        if (any < 0 || any >= H || anx < 0 || anx >= W || d[any][anx]) any = ay, anx = ax;
        if (bny < 0 || bny >= H || bnx < 0 || bnx >= W || d[bny][bnx]) bny = by, bnx = bx;
        if (dist[any][anx][bny][bnx] > dist[ay][ax][by][bx] + 1) {
          dist[any][anx][bny][bnx] = dist[ay][ax][by][bx] + 1;
          que.emplace(any, anx, bny, bnx);
        }
      }
    }
    if (na) cout << "NA" << endl;
  }  

  return 0;
}