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 <cstring>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <cassert>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <functional>
#include <iostream>
#include <map>
#include <set>
using namespace std;
typedef pair<int,int> P;
typedef pair<int,P> P1;
typedef pair<P,P> P2;
typedef long long ll;
#define pu push
#define pb push_back
#define mp make_pair
#define eps 1e-7
#define INF 1000000000
#define fi first
#define sc second
#define rep(i,x) for(int i=0;i<x;i++)
int dp[55][55][55][55];
bool u[55][55][55][55];
int main()
{
	while(1)
	{
		int x,y;
		int ax,ay;
		int bx,by;
		cin >> x >> y; if(x == 0) return 0;
		cin >> ax >> ay;
		cin >> bx >> by; 
		int f[55][55];
		for(int i=0;i<y;i++)
		{
			for(int j=0;j<x;j++)
			{
				cin >> f[i][j];
			}
		}
		for(int i=0;i<55;i++) for(int j=0;j<55;j++) for(int k=0;k<55;k++) for(int l=0;l<55;l++) dp[i][j][k][l] = INF,u[i][j][k][l] = 0;
		dp[ay][ax][by][bx] = 0;
		queue<P2>que;
		que.push(mp(mp(ay,ax),mp(by,bx)));
		while(!que.empty())
		{
			P2 p = que.front(); que.pop();
			if(u[p.fi.fi][p.fi.sc][p.sc.fi][p.sc.sc]) continue;
			u[p.fi.fi][p.fi.sc][p.sc.fi][p.sc.sc] = true;
			int dx[4]={0,1,0,-1};
			int dy[4]={1,0,-1,0};
			for(int k=0;k<4;k++)
			{
				int ny = p.fi.fi+dy[k];
				int nx = p.fi.sc+dx[k];
				if(0<=ny && ny<y && 0<=nx && nx<x && f[ny][nx]==0)
				{
				}
				else
				{
					ny = p.fi.fi;
					nx = p.fi.sc;
				}
				int ny2 = p.sc.fi+dy[(k+2)%4];
				int nx2 = p.sc.sc+dx[(k+2)%4];
				if(0<=ny2 && ny2<y && 0<=nx2 && nx2<x && f[ny2][nx2]==0)
				{
				}
				else
				{
					ny2 = p.sc.fi;
					nx2 = p.sc.sc;
				}
				if(dp[ny][nx][ny2][nx2] > dp[p.fi.fi][p.fi.sc][p.sc.fi][p.sc.sc]+1)
				{
					dp[ny][nx][ny2][nx2] = dp[p.fi.fi][p.fi.sc][p.sc.fi][p.sc.sc]+1;
					que.push(mp(mp(ny,nx),mp(ny2,nx2)));
				}
			}
		}
		int res = INF;
		for(int i=0;i<y;i++) for(int j=0;j<x;j++) res = min(res,dp[i][j][i][j]);
		if(res >= 100) puts("NA");
		else printf("%d\n",res);
	}
}