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 <cstdio>
#include <utility>
#include <queue>
#include <map>
using namespace std;

typedef pair<int,int> __P;
typedef pair<__P,__P> _P;
typedef pair<_P,int> P;

#define C(A,B) (0<=(A)&&(A)<(B))

int main() {
	queue<P> que;
	map<P,bool> mp;
	int X,Y;
	int tx,ty;
	int kx,ky;
	int count;
	int d[50][50];
	int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};
	while(true) {
		scanf("%d %d",&X,&Y);
		if(X==0&&Y==0) break;
		scanf("%d %d",&tx,&ty);
		scanf("%d %d",&kx,&ky);
		tx--;ty--;kx--;ky--;
		for(int i=0;i<Y;i++) {
			for(int j=0;j<X;j++) {
				scanf("%d",&d[j][i]);
			}
		}
		que.push(P(_P(__P(tx,ty),__P(kx,ky)),0));
		count=-1;
		while(que.size()) {
			P& p=que.front();
			tx=p.first.first.first;
			ty=p.first.first.second;
			kx=p.first.second.first;
			ky=p.first.second.second;
			if(p.second>=100) {
				break;
			}
			if(mp[p]==true) {
				break;
			}
			if(tx==kx&&ty==ky) {
				count=p.second;
				break;
			}
			mp[p]=true;
			for(int i=0;i<4;i++) {
				int ntx=tx,nty=ty,nkx=kx,nky=ky;
				if(C(ntx+dx[i],X)&&C(nty+dy[i],Y)&&!d[ntx+dx[i]][nty+dy[i]]) {
					ntx+=dx[i],nty+=dy[i];
				}
				if(C(nkx-dx[i],X)&&C(nky-dy[i],Y)&&!d[nkx-dx[i]][nky-dy[i]]) {
					nkx-=dx[i],nky-=dy[i];
				}
				que.push(P(_P(__P(ntx,nty),__P(nkx,nky)),p.second+1));
			}
			
			que.pop();
		}
		if(count!=-1) {
			printf("%d\n",count);
		}else {
			printf("NA\n");
		}
	}
	return 0;
}