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;
typedef long long ll;

const int INF = 1 << 25;
int dx[4] = { 1, 0, -1, 0 }, dy[4] = { 0, 1, 0, -1 };

int b[50][50];
int dist[50][50][50][50];

int W, H;

bool in(int x, int y) {
	return 0 <= x && x < W && 0 <= y && y < H;
}

struct S {
	int x1, y1, x2, y2, d;
};

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	while(cin >> W >> H, W + H) {
		int sx[2], sy[2];
		for(int i = 0; i < 2; i++) {
			cin >> sx[i] >> sy[i];
			sx[i]--, sy[i]--;
		}
		for(int i = 0; i < H; i++) {
			for(int j = 0; j < W; j++) {
				cin >> b[i][j];
			}
		}

		fill((int*)begin(dist), (int*)end(dist), INF);
		dist[sy[0]][sx[0]][sy[1]][sx[1]];
		queue<S> q;
		q.push({ sx[0], sy[0], sx[1], sy[1], 0 });
		while(q.size()) {
			int x[2] = { q.front().x1, q.front().x2 };
			int y[2] = { q.front().y1, q.front().y2 };
			int d = q.front().d;
			q.pop();
			if(dist[y[0]][x[0]][y[1]][x[1]] < d) continue;
			for(int k = 0; k < 4; k++) {
				int nx[2] = { x[0] + dx[k], x[1] - dx[k] };
				int ny[2] = { y[0] + dy[k], y[1] - dy[k] };
				for(int i = 0; i < 2; i++) {
					if(nx[i] < 0 || W <= nx[i] || b[ny[i]][nx[i]]) nx[i] = x[i];
					if(ny[i] < 0 || H <= ny[i] || b[ny[i]][nx[i]]) ny[i] = y[i];
				}
				if(dist[ny[0]][nx[0]][ny[1]][nx[1]] > d + 1) {
					dist[ny[0]][nx[0]][ny[1]][nx[1]] = d + 1;
					q.push({ nx[0], ny[0], nx[1], ny[1], d + 1 });
				}
			}
		}

		int ans = INF;
		for(int y = 0; y < H; y++) {
			for(int x = 0; x < W; x++) {
				ans = min(ans, dist[x][y][x][y]);
			}
		}
		if(ans != INF) {
			cout << ans << endl;
		}
		else {
			cout << "NA" << endl;
		}
	}
}

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 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;
			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;
				if (c.tx == c.kx&&c.ty == c.ky||c.t >= 100)
				{
					break;
				}
				c.t++;
				rep(i, 4)
				{
					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)
					{
						c.tx += mx[i];
						c.ty += my[i];
						c.kx -= mx[i];
						c.ky -= my[i];
						que.push(c);
						java[c.tx][c.ty][c.kx][c.ky] = 1;
						c.tx -= mx[i];
						c.ty -= my[i];
						c.kx += mx[i];
						c.ky += my[i];
					}
					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)
					{
						c.kx -= mx[i];
						c.ky -= my[i];
						que.push(c);
						java[c.tx][c.ty][c.kx][c.ky] = 1;
						c.kx += mx[i];
						c.ky += my[i];
					}
					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)
					{
						c.tx += mx[i];
						c.ty += my[i];
						que.push(c);
						java[c.tx][c.ty][c.kx][c.ky] = 1;
						c.tx -= mx[i];
						c.ty -= my[i];
					}
				}
			}
			if (c.tx == c.kx&&c.ty == c.ky)
				cout << c.t << endl;
			else
				cout << "NA" << endl;
		}
	return 0;
}