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 <bits/stdc++.h>
using namespace std;

int table[52][52];

bool memo[52][52][52][52];

const int leftmove = -1;
const int rightmove = 1;
const int upmove = -1;
const int downmove = 1;

int main() {

    while(1){

        int w,h;

        //scanf(" %d %d",&w,&h);

        cin >> w >> h;

        if(w==0&&h==0) break;

        int tx,ty,kx,ky;

        //scanf(" %d %d %d %d",&tx,&ty,&kx,&ky);

        cin >> tx >> ty >> kx >> ky;

        for(int i=1;i<52;i++){
            for(int j=1;j<52;j++){
                for(int k=0;k<52;k++){
                    for(int r=0;r<52;r++){
                        memo[i][j][k][r] = false;
                    }
                }
            }
        }

        for(int i=1;i<=h;i++){
            for(int j=1;j<=w;j++){
                //scanf(" %d",&table[i][j]);
                cin >> table[i][j];
            }
        }

        /*printf("\n");

        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                printf("%d ",table[i][j]);
            }
            printf("\n");
        }*/

        //memset(memo,false,sizeof(memo));

        queue<vector<int> > q;

        vector<int> v(5);

        v[0] = tx; v[1] = ty; v[2] = kx; v[3] = ky; v[4] = 0;

        if(table[v[0]][v[1]] == 1 || table[v[2]][v[3]] == 1){
            cout << "NA" << endl;
            continue;
        }

        q.push(v);

        bool check = false;

        while(!q.empty()){

            v = q.front(); q.pop();

            if(v[0] == v[2] && v[1] == v[3]){
                check = true;
                cout << v[4] << endl;
                break;
            }

            memo[v[0]][v[1]][v[2]][v[3]] = true;

            v[4]++;

            if(v[4] >= 100){
                break;
            }

            vector<int> before(5);

            for(int i=0;i<5;i++){
                before[i] = v[i];
            }

            if(v[0]+leftmove != 0 && table[v[0]+leftmove][v[1]] == 0){
                v[0]+=leftmove;
            }
            if(v[2]+rightmove != w+1 && table[v[2]+rightmove][v[3]] == 0){
                v[2]+=rightmove;
            }

            if(!memo[v[0]][v[1]][v[2]][v[3]]) {
                q.push(v);
            }

            for(int i=0;i<5;i++){
                v[i] = before[i];
            }

            if(v[2]+leftmove != 0 && table[v[2]+leftmove][v[3]] == 0){
                v[2]+=leftmove;
            }
            if(v[0]+rightmove != w+1 && table[v[0]+rightmove][v[1]] == 0){
                v[0]+=rightmove;
            }

            if(!memo[v[0]][v[1]][v[2]][v[3]]) {
                q.push(v);
            }


            for(int i=0;i<5;i++){
                v[i] = before[i];
            }

            if(v[3]+upmove != 0 && table[v[2]][v[3]+upmove] == 0){
                v[3]+=upmove;
            }
            if(v[1]+downmove != h+1 && table[v[0]][v[1]+downmove] == 0){
                v[1]+=downmove;
            }

            if(!memo[v[0]][v[1]][v[2]][v[3]]) {
                q.push(v);
            }

            for(int i=0;i<5;i++){
                v[i] = before[i];
            }

            if(v[1]+upmove != 0 && table[v[0]][v[1]+upmove] == 0){
                v[1]+=upmove;
            }
            if(v[3]+downmove != h+1 && table[v[2]][v[3]+downmove] == 0){
                v[3]+=downmove;
            }

            if(!memo[v[0]][v[1]][v[2]][v[3]]) {
                q.push(v);
            }
        }

        if(!check){
            cout << "NA" << endl;
        }



    }

    return 0;
}

C++: #define _USE_MATH_DEFINES
#define INF 10000000
#include <iostream>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <limits>
#include <map>
#include <string>
#include <cstring>
#include <set>
#include <deque>
#include <bitset>
#include <list>

using namespace std;

typedef long long ll;
typedef pair <int,int> P;
typedef pair <P,P> PP;
typedef pair <int,PP> PPP;

static const double eps = 1e-8;

static const int moveTo[][2] = {{1,0},{0,-1},{-1,0},{0,1}};
static const int moveToRev[][2] = {{-1,0},{0,1},{1,0},{0,-1}};

int stage[50][50];

int bfs(int tx,int ty,int kx,int ky,int w,int h){
	priority_queue<PPP,vector<PPP>,greater<PPP> > que;
	que.push(PPP(0,PP(P(tx,ty),P(kx,ky))));	

	int res = INF;
	while(!que.empty()){
		int cost = que.top().first;
		if(res <= cost || cost >= 100){
			que.pop(); continue;
		}

		int tx = que.top().second.first.first;
		int ty = que.top().second.first.second;
		int kx = que.top().second.second.first;
		int ky = que.top().second.second.second;

		if(tx==kx && ty == ky) res = min(res,cost);

		que.pop();

		for(int i=0;i<4;i++){
			int tdx = tx + moveTo[i][0];
			int tdy = ty + moveTo[i][1];
			bitset<2> bit;

			if((tdx < 0 || tdx >= w || tdy < 0 || tdy >=h) || stage[tdy][tdx]) {
				tdx = tx;
				tdy = ty;
				bit[0] = 1;
			}

			int kdx = kx + moveToRev[i][0];
			int kdy = ky + moveToRev[i][1];

			if((kdx < 0 || kdx >= w || kdy < 0 || kdy >=h) || stage[kdy][kdx]) {
				kdx = kx;
				kdy = ky;
				bit[1] = 1;
			}
			if(bit == (1<<2) -1) continue;
			que.push(PPP(cost+1,PP(P(tdx,tdy),P(kdx,kdy))));
		}
	}

	return res;
}

int main(){

	int w,h;
	while(~scanf("%d %d",&w,&h)){
		if(w ==h && h==0) break;
		int tx,ty;
		scanf("%d %d",&tx,&ty);
		int kx,ky;
		scanf("%d %d",&kx,&ky);
		for(int y=0;y<h;y++){
			for(int x=0;x<w;x++){
				scanf("%d",&stage[y][x]);
			}
		}

		int res = bfs(tx,ty,kx,ky,w,h);
		if(res == INF) printf("NA\n");
		else printf("%d\n",res);
	}
}