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<map>
#include<set>
#include<list>
#include<cmath>
#include<queue>
#include<stack>
#include<cstdio>
#include<string>
#include<vector>
#include<complex>
#include<cstdlib>
#include<cstring>
#include<numeric>
#include<sstream>
#include<iostream>
#include<algorithm>
#include<functional>

#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,b,n) for(int i=b;i<n;i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;

const int INF=1<<29;
const double EPS=1e-9;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int X,Y;
int tx,ty;
int kx,ky;
int board[60][60];
typedef pair<pii,pii> P;
queue<P> que;
queue<int> kai;
int main(){
	while(cin>>X>>Y,X||Y){
		cin>>tx>>ty;
		cin>>kx>>ky;
		while(!kai.empty()){
			kai.pop();
		}
		while(!que.empty()){
			que.empty();
		}
		rep(i,Y+1){
			rep(j,X+1){
				board[i][j] = 0;
			}
		}

		for(int i = 1;i <= Y;i++){
			for(int j  =1;j <= X;j++){
				cin>>board[i][j];
			}
		}
		/*for(int i = 1;i <= Y;i++){
			for(int j  =1;j <= X;j++){
				cout<<board[i][j];
			}
			cout <<endl;
		}*/
		que.push(P(pii(tx,ty),pii(kx,ky)));
		kai.push(0);
		int ans = 200;
		map<P,int> ma;
		ma.clear();
		int mm = 0;
		while(!que.empty()){
			int ptx = que.front().first.first;
			int pty = que.front().first.second;
			int pkx = que.front().second.first;
			int pky = que.front().second.second;
			int sum = kai.front();
			que.pop();
			kai.pop();
			//cout <<sum<<endl;
			if(sum>=100){
				continue;
			}
			if(ptx==pkx&&pty==pky){
				ans = min(ans,sum);
				continue;
			}
			ma[P(pii(ptx,pty),pii(pkx,pky))] = 1;
			ma[P(pii(pkx,pky),pii(ptx,pty))] = 1;
			for(int i = 0;i < 4;i++){
				int ntx =ptx +dx[i];
				int nty =pty +dy[i];
				int nkx =pkx +dx[(i+2)%4];
				int nky =pky+dy[(i+2)%4];
				if(ma[P(pii(ntx,nty),pii(nkx,nky))] ==1||ma[P(pii(nkx,nky),pii(ntx,nty))]==1){
					continue;
				}
				if(ntx>X||ntx<=0||nty>Y||nty<=0||board[nty][ntx]==1){
					nty = pty;
					ntx = ptx;

					//cout <<nty<<" "<<ntx<<endl;
				}
				if(nky>Y||nky<=0||nkx>X||nkx<=0||board[nky][nkx]==1){
					nky = pky;
					nkx = pkx;
				}
				if(ma[P(pii(ntx,nty),pii(nkx,nky))] ==1||ma[P(pii(nkx,nky),pii(ntx,nty))]==1){
					continue;
				}
				ma[P(pii(ntx,nty),pii(nkx,nky))] = 1;
				ma[P(pii(nkx,nky),pii(ntx,nty))] = 1;
				que.push(P(pii(ntx,nty),pii(nkx,nky)));
				kai.push(sum+1);
			}
		}
		if(ans==200){
			cout<<"NA"<<endl;
		}else{
			cout <<ans<<endl;
		}
	}
	return 0;
}