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 {
				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<stdio.h>
#include<iostream>
#include<queue>
#include<string.h>
using namespace std;
struct Y{
int hx,hy,rx,ry,tim;
};
int mp[52][52],vh[52][52],vr[52][52];
int main(){
int n,w,h,i,j,a[2]={1,-1},b[2],g,k;
Y e;
while(1){
queue<Y> q;
	g=0;
	k=0;
	cin>>w>>h;
	if(w==0&&h==0)break;
	cin>>e.hx>>e.hy>>e.rx>>e.ry;
	e.tim=0;
	q.push(e);
	memset(mp,0,sizeof(mp));
	memset(vh,0,sizeof(vh));
	memset(vr,0,sizeof(vr));
	for(i=0;i<=h+1;i++){
		mp[i][0]=1;
		mp[i][w+1]=1;
	}
	for(i=0;i<=w+1;i++){
		mp[0][i]=1;
		mp[h+1][i]=1;
	}
	for(i=1;i<=h;i++){
		for(j=1;j<=w;j++){
			cin>>mp[j][i];
			if(mp[j][i]==1)k++;
		}
	}
	while(!q.empty()){
		e=q.front();
		q.pop();
				if(vh[e.hy][e.hx]==0&&vr[e.hy][e.hx]==0)g++;
				if(vr[e.ry][e.rx]==0&&vh[e.ry][e.rx]==0)g++;
				vh[e.hy][e.hx]=1;
				vr[e.ry][e.rx]=2;
		if(e.tim>=100||e.hx==e.rx&&e.hy==e.ry||g==w*h-k)break;
		e.tim++;
		for(i=0;i<2;i++){
			if(mp[e.hy+a[i]][e.hx]!=1&&vh[e.hy+a[i]][e.hx]!=1&&vr[e.ry-a[i]][e.rx]!=2||mp[e.ry-a[i]][e.rx]!=1&&vr[e.ry-a[i]][e.rx]!=2&&vh[e.hy+a[i]][e.hx]!=1){
				b[0]=0;
				b[1]=0;
				if(mp[e.hy+a[i]][e.hx]!=1){
					e.hy+=a[i];
					b[0]=1;
				}
				if(mp[e.ry-a[i]][e.rx]!=1){
					e.ry-=a[i];
					b[1]=1;
				}
				if(vh[e.hy][e.hx]==0&&vr[e.hy][e.hx]==0)g++;
				if(vr[e.ry][e.rx]==0&&vh[e.ry][e.rx]==0)g++;
				vh[e.hy][e.hx]=1;
				vr[e.ry][e.rx]=2;
				q.push(e);
				if(b[0]==1)e.hy-=a[i];
				if(b[1]==1)e.ry+=a[i];
			}																									
			if(mp[e.hy][e.hx+a[i]]!=1&&vh[e.hy][e.hx+a[i]]!=1&&vr[e.ry][e.rx-a[i]]!=2||mp[e.ry][e.rx-a[i]]!=1&&vr[e.ry][e.rx-a[i]]!=2&&vh[e.hy][e.hx+a[i]]!=1){
				b[0]=0;
				b[1]=0;
				if(mp[e.hy][e.hx+a[i]]!=1){
					e.hx+=a[i];
					b[0]=1;
				}
				if(mp[e.ry][e.rx-a[i]]!=1){
					e.rx-=a[i];
					b[1]=1;
				}
				if(vh[e.hy][e.hx]==0&&vr[e.hy][e.hx]==0)g++;
				if(vr[e.ry][e.rx]==0&&vh[e.ry][e.rx]==0)g++;
				vh[e.hy][e.hx]=1;
				vr[e.ry][e.rx]=2;
				q.push(e);
				if(b[0]==1)e.hx-=a[i];
				if(b[1]==1)e.rx+=a[i];
			}
		}
		e.tim--;
	}
	if(e.tim>=100||g==w*h-k)printf("NA\n");
	else cout<<e.tim<<endl;
}
return 0;
}

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;

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(d == 99) break;
			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[y][x][y][x]);
			}
		}
		if(ans != INF) {
			cout << ans << endl;
		}
		else {
			cout << "NA" << endl;
		}
	}
}