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(102)
	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]
			}
			if now==next {
				continue
			}
			next.Turn += 1
			if next.Turn <= 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				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;

bool went[50 + 10][50 + 10][50 + 10][50 + 10] = { 0 };

int map[50 + 10][50 + 10] = { 0 };

int gx[] = { 1,0,-1,0,-1,0,1,0 };
int gy[] = { 0,1,0,-1,0,-1,0,1 };

struct ST
{
	int tx, ty;
	int kx, ky;
	int tim=0;
};

bool ChekNow(ST);


ST GoMap(ST, int);


int main()
{
	ST now,tmp;

	queue <ST> nx;


	int w, h;
	int tsx, tsy;
	int ksx, ksy;

	bool flg;
	int i, j;

	while (cin >> w >> h, w != 0 && h != 0)
	{
		flg = true;

		cin >> tsx >> tsy;
		cin >> ksx >> ksy;
		
		for (i = 1; i <= h; i++)
		{
			map[i][0] = map[i][w + 1] = 1;

			for (j = 1; j <= w; j++)
			{
				cin >> map[i][j];
			}
		}

		for (i = 0; i <= w + 1; i++)
		{
			map[0][i] = 1;
			map[h + 1][i] = 1;
		}


		now.tx = tsx;
		now.ty = tsy;
		now.kx = ksx;
		now.ky = ksy;
		now.tim = 0;

		nx.push(now);

		while (!nx.empty() && tmp.tim<100)
		{
			now = nx.front();
			nx.pop();

			if (ChekNow(now))
			{
				continue;
			}
			went[now.tx][now.ty][now.kx][now.ky] = true;

			if (now.tx == now.kx && now.ty == now.ky)
			{
				cout << now.tim << endl;

				flg = false;

				break;
			}

			for (i = 0; i < 4; i++)
			{
				tmp=GoMap(now, i);

				if (!ChekNow(tmp))
				{
					tmp.tim++;
					nx.push(tmp);
				}
			}
		}

		if (flg)
		{
			cout << "NA\n";
		}

		while (!nx.empty())
		{
			nx.pop();
		}
	}
	return 0;
}


bool ChekNow(ST ex)
{
	return went[ex.tx][ex.ty][ex.kx][ex.ky];
}


ST GoMap(ST ex, int i)
{
	if (map[ex.ty + gy[i]][ex.tx + gx[i]] == 0)
	{
		ex.ty += gy[i];
		ex.tx += gx[i];
	}
	if (map[ex.ky + gy[i + 4]][ex.kx + gx[i + 4]] == 0)
	{
		ex.ky += gy[i + 4];
		ex.kx += gx[i + 4];
	}

	return ex;
}

C++: #include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstring>
#include <sstream>
using namespace std;
static const double EPS = 1e-5;
typedef long long ll;
typedef pair<int,int> pi;
#define rep(i,n) for(int i=0;i<n;i++)


int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};
bool past[50][50][50][50];
int d[50][50];
int x,y;
int tx,ty,kx,ky;


main(){
	while(cin>>x>>y,x){
		cin>>tx>>ty>>kx>>ky;
		--tx;
		--ty;
		--kx;
		--ky;
		memset(d,0,sizeof(d));
		rep(i,x)rep(j,y)cin>>d[i][j];
		
		queue<pair<pair<pi,pi>,int> > state;
		memset(past,0,sizeof(past));
		
		state.push(make_pair(make_pair(make_pair(tx,ty),make_pair(kx,ky)),0));
		
		past[tx][ty][kx][ky]=1;
		
		int time=0;
		bool na=true;
		
		while(!state.empty()){
			pair<pi,pi> tp=state.front().first;
			time=state.front().second;
			state.pop();
			if(time>=100)break;
			if(tp.first==tp.second){
				na=false;
				break;
			}
			
			rep(i,4){
				int ttx=tp.first.first+dx[i],tty=tp.first.second+dy[i],
					tkx=tp.second.first-dx[i],tky=tp.second.second-dy[i];
				
				if(ttx<0 || ttx>=x || tty<0 || tty>=y || d[ttx][tty]==1){
					ttx-=dx[i];
					tty-=dy[i];
				}
				if(tkx<0 || tkx>=x || tky<0 || tky>=y || d[tkx][tky]==1){
					tkx+=dx[i];
					tky+=dy[i];
				}
				pair<pair<int,int>,pair<int,int> > next=make_pair(make_pair(ttx,tty),make_pair(tkx,tky));
				
				if(past[ttx][tty][tkx][tky])continue;
				past[ttx][tty][tkx][tky]=1;
				state.push(make_pair(next,time+1));
			}
		}
		
		if(na)puts("NA");
		else cout<<time<<endl;
	}
}

C++: #include <iostream>
#include <queue>
#define rep2(x,from,to) for(int x=(from);(x)<(to);(x)++)
#define rep(x,to) rep2(x,0,to)
using namespace std;
bool mem[52][52][52][52] = {{{{}}}};
struct S{
	int a,b,c,d,t;
};
int dx[4] = {-1,0,1,0};
int dy[4] = {0,1,0,-1};
void init() {
	memset(mem,0,sizeof(mem));
}
int main(){
	int x, y, tx, ty, kx, ky, k;
	while(cin >> x >> y, (x || y)) {
		int b[52][52] = {};
		init();
		cin >> tx >> ty >> kx >> ky;
		rep(i,y) {
			rep(j,x) {
				cin >> k;
				b[i+1][j+1] = 1-k;
			}
		}
		queue<S> q;
		S s = {tx,ty,kx,ky,0};
		q.push(s);
		while(!q.empty()) {
			S s = q.front();
			if(q.front().t >= 100) break;
			if(s.a==s.c&&s.b==s.d) break;
			q.pop();
			if(mem[s.a][s.b][s.c][s.d]++) continue;
			rep(i,4) {
				int na = s.a+dx[i], nb = s.b+dy[i], nc = s.c+dx[(i+2)%4], nd = s.d+dy[(i+2)%4];
				if(!b[nb][na]&&!b[nd][nc]) continue;
				if(!b[nb][na]) na = s.a, nb = s.b;
				if(!b[nd][nc]) nc = s.c, nd = s.d;
				S ns = {na, nb, nc, nd, s.t+1};
				q.push(ns);
			}
		}
		if(q.empty()) cout << "NA" << endl;
		else if(q.front().t >= 100) cout << "NA" << endl;
		else cout << q.front().t << endl;
	}
}