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>
using namespace std;

const int INF =100000000;

class Point{
public:
  int tx;
  int ty;
  int kx;
  int ky;
};

int main(){
  int N,M;
  while(cin>>N>>M,N || M){
      int o_tx,o_ty;
      int o_kx,o_ky;
      cin>>o_tx>>o_ty;
      cin>>o_kx>>o_ky;
      int F[52][52];
      for(int y=0;y<=N+1;y++){
        for(int x=0;x<=M+1;x++){
          F[y][x]=1;
        }
      }

      for(int y=1;y<=N;y++){
        for(int x=1;x<=M;x++){
          cin>>F[y][x];
        }
      }

      int D[52][52];
      for(int y=1;y<=N;y++){
        for(int x=1;x<=M;x++){
          D[y][x]=INF;
        }
      }
      bool same_pos[52][52][52][52];
      for(int i=1;i<=N;i++){
        for(int j=1;j<=M;j++){
          for(int k=1;k<=N;k++){
            for(int q=1;q<=M;q++){
              same_pos[i][j][k][q]=false;
            }
          }
        }
      }
      queue<Point> que;
      Point p;
      p.tx=o_tx;p.ty=o_ty;
      p.kx=o_kx;p.ky=o_ky;
      que.push(p);
      D[p.ty][p.tx]=0;

      while(!que.empty()){
        p=que.front();que.pop();
        if(same_pos[p.ty][p.tx][p.ky][p.kx])continue;
        same_pos[p.ty][p.tx][p.ky][p.kx]=true;
        if(D[p.ty][p.tx]==100)break;
        if(p.tx==p.kx&&p.ty==p.ky){
          cout<<D[p.ty][p.tx]<<endl;
          break;
        }
        if(F[p.ty-1][p.tx]!=1 || F[p.ky+1][p.kx]!=1){
          Point q;
          if(F[p.ty-1][p.ty]!=1){
            q.tx=p.tx;q.ty=p.ty-1;
          }
          else{
            q.tx=p.tx;q.ty=p.ty;
          }
          if(F[p.ky+1][p.kx]!=1){
            q.kx=p.kx;q.ky=p.ky+1;
          }
          else{
            q.kx=p.kx;q.ky=p.ky;
          }
          que.push(q);
          D[q.ty][q.tx]=D[p.ty][p.tx]+1;

        }
        if(F[p.ty+1][p.tx]!=1 || F[p.ky-1][p.kx]!=1){
          Point q;
          if(F[p.ty+1][p.tx]!=1){
            q.tx=p.tx;q.ty=p.ty+1;
          }
          else{
            q.tx=p.tx;q.ty=p.ty;
          }
          if(F[p.ky-1][p.kx]!=1){
            q.kx=p.kx;q.ky=p.ky-1;
          }
          else{
            q.kx=p.kx;q.ky=p.ky;
          }
          que.push(q);
          D[q.ty][q.tx]=D[p.ty][p.tx]+1;
        }
        if(F[p.ty][p.tx-1]!=1 || F[p.ky][p.kx+1]!=1){
          Point q;
          if(F[p.ty][p.tx-1]!=1){
            q.tx=p.tx-1;q.ty=p.ty;
          }
          else{
            q.tx=p.tx;q.ty=p.ty;
          }
          if(F[p.ky][p.kx+1]!=1){
            q.kx=p.kx+1;q.ky=p.ky;
          }
          else{
            q.kx=p.kx;q.ky=p.ky;
          }
          que.push(q);
          D[q.ty][q.tx]=D[p.ty][p.tx]+1;
        }
        if(F[p.ty][p.tx+1]!=1 || F[p.ky][p.kx-1]!=1){
          Point q;
          if(F[p.ty][p.tx+1]!=1){
            q.tx=p.tx+1;q.ty=p.ty;
          }
          else{
            q.tx=p.tx;q.ty=p.ty;
          }
          if(F[p.ky][p.kx-1]!=1){
            q.kx=p.kx-1;q.ky=p.ky;
          }
          else{
            q.kx=p.kx;q.ky=p.ky;
          }
          que.push(q);
          D[q.ty][q.tx]=D[p.ty][p.tx]+1;
        }
      }
      if(p.tx!=p.kx || p.ty!=p.ky){
        cout<<"NA"<<endl;
      }
    }
  return 0;
}

C++: const int dx[][4] = {{1, 0, -1, 0}, {-1, 0, 1, 0}};
const int dy[][4] = {{0, 1, 0, -1}, {0, -1, 0, 1}};

int X, Y;

bool map[50][50];
bool passed[50][50][50][50];

struct P
{
    int tx, ty;
    int kx, ky;
    int cost;

    P(int _tx, int _ty, int _kx, int _ky, int _cost) : tx(_tx), ty(_ty), kx(_kx), ky(_ky), cost(_cost) {};
};

bool check(int x, int y)
{
    return x < 0 || x >= X || y < 0 || y >= Y || map[y][x];
}

int main()
{
    int tx, ty, kx, ky, ans;
    while(cin >> X >> Y, X|Y)
    {
        ans = -1;
        memset(passed, 0, sizeof passed);
        queue<P> que;

        cin >> tx >> ty >> kx >> ky;
        tx--, ty--, kx--, ky--;

        for(int i = 0; i < Y; i++)
            for(int j = 0; j < X; j++)
                cin >> map[i][j];

        passed[tx][ty][kx][ky] = true;

        for(que.push(P(tx, ty, kx, ky, 0)); !que.empty(); que.pop())
        {
            P p = que.front();

            if(p.cost >= 100)
                break;

            if(p.tx == p.kx && p.ty == p.ky)
            {
                ans = p.cost;
                break;
            }

            for(int i = 0; i < 4; i++)
            {
                int mtx = p.tx + dx[0][i], mty = p.ty + dy[0][i];
                int mkx = p.kx + dx[1][i], mky = p.ky + dy[1][i];

                if(check(mtx, mty))
                    mtx = p.tx, mty = p.ty;
                if(check(mkx, mky))
                    mkx = p.kx, mky = p.ky;
                if(passed[mtx][mty][mkx][mky])
                    continue;

                passed[mtx][mty][mkx][mky] = true;
                que.push(P(mtx, mty, mkx, mky, p.cost + 1));
            }
        }

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