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)
	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 < 100-1 {
				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<cstdio>
#include<iostream>
#include<algorithm>
#include<math.h>
#include<queue>
#include<string.h>
#include<string>
#include<vector>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
struct X
{
	int tx, ty, t, kx, ky;
};
int java[51][51][51][51] = { 0 };

int check(int, int, int, int, int, int, int, int);

int main()
{
	int w, h, map[52][52] = { 0 };
		int mx[4] = { 0,1,0,-1 }, my[4] = { 1,0,-1,0 };
		while (1)
		{
			queue<X> que;
			X c,as;
			cin >> w >> h;
			if (w == 0 && h == 0)
				break;
			memset(java, 0, sizeof(java));
			cin >> c.tx >> c.ty >> c.kx >> c.ky;
			c.t = 0;
			que.push(c);
			rep1(i, h)
			{
				rep1(j, w)
				{
					cin >> map[i][j];
				}
			}
			/*?£???????*/
			rep(i, h + 2)//n???????????°,m????¨??????°
			{
				map[i][0] = 1;
				map[i][w + 1] = 1;
			}
			rep(i, w + 2)
			{
				map[0][i] = 1;
				map[h + 1][i] = 1;
			}
			while (!que.empty())
			{
				c = que.front();
				que.pop();
				java[c.tx][c.ty][c.kx][c.ky] = 1;

			//	c.t++;

				if (c.tx == c.kx&&c.ty == c.ky||c.t >= 100)
				{
					break;
				}
				
				rep(i, 4)
				{
					as = c;

					if (check(c.tx, c.ty, c.kx, c.ky, mx[i], my[i], h, w) == 1)
					{
						if (java[c.tx + mx[i]][c.ty + my[i]][c.kx - mx[i]][c.ky - my[i]] == 0 && map[c.tx + mx[i]][c.ty + my[i]] == 0 && map[c.kx - mx[i]][c.ky - my[i]] == 0)
						{
							++as.t;

							as.tx = c.tx + mx[i];
							as.ty = c.ty + my[i];
							as.kx = c.kx - mx[i];
							as.ky = c.ky - my[i];
							que.push(as);
							java[as.tx][as.ty][as.kx][as.ky] = 1;
						}
						else if (java[c.tx][c.ty][c.kx - mx[i]][c.ky - my[i]] == 0 && map[c.tx /*+ mx[i]*/][c.ty /*+ my[i]*/] != 0 && map[c.kx - mx[i]][c.ky - my[i]] == 0)
						{
							++as.t;

							as.kx = c.kx - mx[i];
							as.ky = c.ky - my[i];
							que.push(as);
							java[as.tx][as.ty][as.kx][as.ky] = 1;
						}
						else if (java[c.tx + mx[i]][c.ty + my[i]][c.kx][c.ky] == 0 && map[c.tx + mx[i]][c.ty + my[i]] == 0 && map[c.kx /*- mx[i]*/][c.ky /*- my[i]*/] != 0)
						{
							++as.t;

							as.tx = c.tx + mx[i];
							as.ty = c.ty + my[i];
							que.push(as);
							java[as.tx][as.ty][as.kx][as.ky] = 1;
						}
					}
				}
			}
			if (c.tx == c.kx&&c.ty == c.ky)
				cout << c.t << endl;
			else
				cout << "NA" << endl;
		}
	return 0;
}


int check(int tx, int ty, int kx, int ky, int mx, int my ,int h ,int w )
{
	tx += mx;
	kx -= mx;

	ty += my;
	ky -= my;

	if (tx > w || kx > w || ty > h || ky > h || tx < 1 || kx < 1 || ty < 1 || ky < 1)
	{
		return 0;
	}

	return 1;
}

C++: #include <iostream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
#include <set>

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,j) FOR(i,0,j)
#define mp std::make_pair

typedef long long ll;
typedef unsigned long long ull;
typedef std::pair<int,int> P;
typedef std::pair<int,std::pair<P,P>> State;

const int INF = 1001001001;

// S N E W(南北東西)
const int dx[8] = {0, 0, 1, -1, 1, 1, -1, -1}, dy[8] = {1, -1, 0, 0, 1, -1, 1, -1};

int X, Y;
int tx, ty, kx, ky;
int map[50][50], d[50][50][50][50];

int main(){
    while(scanf("%d %d", &X, &Y), X || Y){
        scanf("%d %d %d %d", &tx, &ty, &kx, &ky);
        tx -= 1; ty -= 1; kx -= 1; ky -= 1;

        REP(i, Y){
            REP(j, X){
                scanf("%d", &map[i][j]);
            }
        }

        REP(i, X){
            REP(j, Y){
                REP(k, X){
                    REP(l, Y){
                        d[i][j][k][l] = INF;
                    }
                }
            }
        }

        std::queue<State> q;
        d[tx][ty][kx][ky] = 0;
        q.push(mp(0, mp(mp(tx, ty), mp(kx, ky))));

        int res = INF;
        while(!q.empty()){
            State s = q.front(); q.pop();
            int t = s.first, x1 = s.second.first.first, y1 = s.second.first.second,
                x2 = s.second.second.first, y2 = s.second.second.second;

            if(t >= 100){continue;}
            if(x1 == x2 && y1 == y2){res = std::min(res, t); continue;}
            if(t > d[x1][y1][x2][y2]){continue;}

            REP(i, 4){
                int nx1 = x1 + dx[i], ny1 = y1 + dy[i],
                    nx2 = x2 - dx[i], ny2 = y2 - dy[i];

                if(X <= nx1 || nx1 < 0 || Y <= ny1 || ny1 < 0 ||
                   map[ny1][nx1] == 1){
                    nx1 = x1; ny1 = y1;
                }

                if(X <= nx2 || nx2 < 0 || Y <= ny2 || ny2 < 0 ||
                   map[ny2][nx2] == 1){
                    nx2 = x2; ny2 = y2;
                }

                if(t + 1 < d[nx1][ny1][nx2][ny2]){
                    d[nx1][ny1][nx2][ny2] = t + 1;
                    q.push(mp(d[nx1][ny1][nx2][ny2], mp(mp(nx1, ny1), mp(nx2, ny2))));
                }
            }
        }

        if(res == INF){
            puts("NA");
        }else{
            printf("%d\n", res);
        }
    }
}