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 <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <time.h>
 
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef int ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<pr,pr> ppr;
typedef priority_queue<pr,Vpr, greater<pr> > PQ;
const int SIZE=1e+5 + 1;
const ut INF=1<<30;
const ld eps=1e-6;
const LL mod=1e+9 + 7;

int tdx[] = {0, 1, 0, -1}, tdy[] = {-1, 0, 1, 0};
int kdx[] = {0, -1, 0, 1}, kdy[] = {1, 0, -1, 0};

int W, H;
int maze[64][64];

typedef struct State {
	int tx, ty, kx, ky, d;
	State(int tx, int ty, int kx, int ky, int d) : tx(tx), ty(ty), kx(kx), ky(ky), d(d){}
	
	bool operator < (const State s) const {
		if(tx != s.tx) return tx < s.tx;
		if(ty != s.ty) return ty < s.ty;
		if(kx != s.kx) return kx < s.kx;
		if(ky != s.ky) return ky < s.ky;
		return false;
	}
} State;

bool check(int x, int y){
	return x >= 0 && x < W && y >= 0 && y < H && maze[y][x] == 0;	
}

int main() {
	while(cin >> W >> H && W){
		int tx, ty, kx, ky;
		memset(maze, 0, sizeof(maze));
		cin >> tx >> ty >> kx >> ky;
		tx--; ty--; kx--; ky--;
		REP(i,H)REP(j,W)
			scanf("%d", &maze[i][j]);
			
		queue<State> que;
		que.push(State(tx, ty, kx, ky, 0));
		map<State, bool> visited;
		bool ok = false;
		while(!que.empty()){
			State s = que.front(); que.pop();
			if(s.d >= 100)
				continue;
			if(s.tx == s.kx && s.ty == s.ky){
				cout << s.d << endl;
				ok = true;
				break;
			}
			REP(i,4){
				int ntx = s.tx + tdx[i], nty = s.ty + tdy[i];
				int nkx = s.kx + kdx[i], nky = s.ky + kdy[i];
				if(!check(ntx, nty)){
					ntx = s.tx;
					nty = s.ty;
				}
				if(!check(nkx, nky)){
					nkx = s.kx;
					nky = s.ky;
				}
				State nState = State(ntx, nty, nkx, nky, 0);
				if(!visited[nState]){
					visited[nState] = true;
					nState.d = s.d + 1;
					que.push(nState);
				}
			}
		}
		if(!ok)
			cout << "NA" << endl;
	}
  return 0;
}