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)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]int64, 0)
	ans := int64(101)
	for pq.Len() > 0 {
		//now := heap.Pop(&pq).(*Status)
		now := pq.Pop().(*Status)
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if v, ok := memo[now.Person]; ok && v <= now.Turn {
			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 += 1
			if next.Turn < 100 {
				//heap.Push(&pq, next)
				pq.Push(next)
			}
		}
	}
	if ans == 101 {
		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<queue>
#include<cstdio>

#define	mp	make_pair

using namespace std;

typedef	pair<int,int>	pii;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int w,h;
unsigned char board[50][50],memo[50][50][50][50];

int main(){
	for(;scanf("%d%d",&w,&h),w;){
		int tx,ty,kx,ky;	scanf("%d%d%d%d",&tx,&ty,&kx,&ky);
		for(int i=0;i<h;i++)for(int j=0;j<w;j++)	scanf("%d",board[i]+j);
		for(int i=0;i<h;i++)for(int j=0;j<w;j++)for(int k=0;k<h;k++)for(int l=0;l<w;l++)	memo[i][j][k][l]=255;

		int ans=-1;
		memo[ty][tx][ky][kx]=0;
		queue< pair<pii,pii> > qu;	qu.push(mp(mp(ty,tx),mp(ky,kx)));
		while(!qu.empty()){
			pair<pii,pii> a=qu.front();	qu.pop();
			int tx=a.first.second, ty=a.first.first;
			int kx=a.second.second,ky=a.second.first;
			int cost=memo[ty][tx][ky][kx];
			if(cost>=100)	break;
			if(ty==ky && tx==kx){
				ans=cost;
				break;
			}
			for(int i=0;i<4;i++){
				int txx=tx+dx[i],tyy=ty+dy[i];
				int kxx=kx-dx[i],kyy=ky-dy[i];
				if(!(0<=txx && txx<w && 0<=tyy && tyy<h && !board[tyy][txx]))	txx=tx,tyy=ty;
				if(!(0<=kxx && kxx<w && 0<=kyy && kyy<h && !board[kyy][kxx]))	kxx=kx,kyy=ky;
				if(cost+1<memo[tyy][txx][kyy][kxx]){
					memo[tyy][txx][kyy][kxx]=cost+1;
					qu.push(mp(mp(tyy,txx),mp(kyy,kxx)));
				}
			}
		}

		printf(~ans?"%d\n":"NA\n",ans);
	}

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