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 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<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;
	}
	*/

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

	return 1;
}

C++: #include<iostream>
#include<queue>
#include<string.h>
#include<cstring>
using namespace std;
struct PP{
	int kx;
	int ky;
	int tx;
	int ty;
	int Z;
};
int w,h;
PP S;
int A[52][52][52][52],D[52][52];
int main(){
	queue<PP> P;
	int d=0,i=0,j=0,l=-1;
	int tx[4]={ 1, 0,-1,0 };       
	int kx[4]={-1, 0, 1,0 };
	int ty[4]={ 0, 1, 0,-1 };
	int ky[4]={ 0, -1, 0,1};
	cin>>w>>h;
	while(w!=0||h!=0){
	memset(A,0,sizeof(A));
		for(i=0;i<=h+1;i++){
		for(j=0;j<=w+1;j++){
		D[i][j]=1;
		}
	}

	cin>>S.tx>>S.ty;
	cin>>S.kx>>S.ky;
	for(i=1;i<=h;i++){
		for(j=1;j<=w;j++){
		cin>>D[i][j];
		}
	}
	S.Z=0;
	P.push(S);
		if(S.tx==S.kx&&S.ty==S.ky){
			d=-1;
			cout<<S.Z;
		}
	while(d!=-1){
		l++;
		if(l==4){
		l=0;
		S=P.front();
		P.pop();
		if(P.empty()){
			cout<<"NA"<<endl;
		break;
		}
		}
		S=P.front();
		
		S.tx=S.tx+tx[l];
		S.ty=S.ty+ty[l];
		S.kx=S.kx+kx[l];
		S.ky=S.ky+ky[l];
		if(A[S.ty][S.tx][S.ky][S.kx]==1){
			continue;
		}
		A[S.ty][S.tx][S.ky][S.kx]=1;
		if(D[S.ty][S.tx]==1){
		S.tx=S.tx-tx[l];
		S.ty=S.ty-ty[l];
		}
		if(D[S.ky][S.kx]==1){
		S.kx=S.kx-kx[l];
		S.ky=S.ky-ky[l];
		}
		//saka();
		S.Z++;
		P.push(S);
		if(S.tx==S.kx&&S.ty==S.ky){
			cout<<S.Z<<endl;
			break;
		}	
		if(S.Z==101){
			cout<<"NA"<<endl;
		break;
		}
	
		
	}
	while(!P.empty()){
	P.pop();
	}
	d=0;
	l=-1;
	cin>>w>>h;
	}	
	return 0;

}

C++: #include<queue>
#include<stdio.h>

using namespace std;

class T{
	public:
	int x1,x2,y1,y2,count;
	T(int x1,int y1,int x2,int y2,int count):x1(x1),y1(y1),x2(x2),y2(y2),count(count){}
};

char check[55][55][55][55];
int board[55][55];

int main(){
	while(1){
		for(int i=0;i<55;i++){
			for(int j=0;j<55;j++){
				board[i][j]=0;
				for(int k=0;k<55;k++){
					for(int p=0;p<55;p++){
						check[i][j][k][p]=0;
					}
				}
			}
		}
		
		int w,h;
		int sx1,sx2,sy1,sy2;
		
		scanf("%d%d",&w,&h);
		if(w==0 && h==0)break;
		
		scanf("%d%d%d%d",&sx1,&sy1,&sx2,&sy2);
		
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				scanf("%d",&board[i][j]);
			}
		}
		
		
		queue<T> que;
		que.push(T(sx1-1,sy1-1,sx2-1,sy2-1,0));
		
		while(1){
			if(que.empty())break;
			
			T u = que.front();
			que.pop();
			
			if(check[u.x1][u.y1][u.x2][u.y2]==1)continue;
			check[u.x1][u.y1][u.x2][u.y2]=1;
			
			if(u.count>=100)break;
			if(u.x1 == u.x2 && u.y1 == u.y2){
				printf("%d\n",u.count);
				goto A;
			}
			
			int dx[4] = {0,1,0,-1};
			int dy[4] = {1,0,-1,0};
			for(int i=0;i<4;i++){
				int nx1 = u.x1 + dx[i];
				int ny1 = u.y1 + dy[i];
				
				int nx2 = u.x2 - dx[i];
				int ny2 = u.y2 - dy[i];
				
				if(nx1<0 || ny1<0 || nx1>=w || ny1>=h || board[ny1][nx1]==1){
					nx1=u.x1;
					ny1=u.y1;
				}
				if(nx2<0 || ny2<0 || nx2>=w || ny2>=h || board[ny2][nx2]==1){
					nx2=u.x2;
					ny2=u.y2;
				}
				que.push(T(nx1,ny1,nx2,ny2,u.count+1));
			}
		}
		
		printf("NA\n");
		A:;
	}
}