Go: package main

import (
	"fmt"
	"math"
	"container/heap"
)

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 ans <= now.Turn {
			continue
		}
		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 <sstream>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
using namespace std;

typedef istringstream ISS;
typedef ostringstream OSS;
typedef vector<string> VS;
typedef int INT;
typedef vector<INT> VI;
typedef vector<VI> VVI;
typedef pair <INT, INT> II;
typedef vector <II> VII;

template<class T> ostream& operator << ( ostream& os, vector<T> v ) {
    for ( typename vector<T>::iterator it_i = v.begin(); it_i != v.end(); ++it_i ) {
        os << *it_i << ", ";
    }
    return os;
}


const int NONE = -1;
int h, w;
int str, stc, skr, skc;
bool T[51][51];

void input() {
    cin >> stc >> str >> skc >> skr;
    stc --;
    str --;
    skc --;
    skr --;
    for ( int i = 0; i < h; ++ i ) {
        for ( int j = 0; j < w; ++ j ) {
            int t;
            cin >> t;
            T[i][j] = t ? true : false;
        }
    }
}

bool check( int r, int c ) {
    if ( r < 0 || r >= h || c < 0 || c >= w ) return false;
    return ! T[r][c];
}

typedef pair <II, II> POS;
typedef pair <int, POS> NODE;
typedef priority_queue <NODE, vector<NODE>, greater<NODE> > QUEUE;
const int dr[4] = { 0, 0, 1, -1 };
const int dc[4] = { 1, -1, 0, 0 };
int MC[51][51][51][51];

int solve() {
    QUEUE Q;
    Q.push( NODE( 0, POS( II( str, stc ), II( skr, skc ) ) ) );
    fill( (int*)MC, (int*)MC+51*51*51*51, INT_MAX );
    MC[str][stc][skr][skc] = 0;

    while ( ! Q.empty() ) {
        NODE node = Q.top();
        Q.pop();

        int steps = node.first;
        int tr = node.second.first.first;
        int tc = node.second.first.second;
        int kr = node.second.second.first;
        int kc = node.second.second.second;

        if ( steps >= 100 ) return NONE;
        if ( kr == tr && kc == tc ) return steps;

        for ( int i = 0; i < 4; ++ i ) {
            int nSteps = steps + 1;
            int ntr = tr + dr[i];
            int ntc = tc + dc[i];
            int nkr = kr + dr[i] * -1;
            int nkc = kc + dc[i] * -1;
            if ( ! check( ntr, ntc ) ) {
                ntr = tr;
                ntc = tc;
            }
            if ( ! check( nkr, nkc ) ) {
                nkr = kr;
                nkc = kc;
            }
            if ( nSteps >= MC[ntr][ntc][nkr][nkc] ) continue;
            MC[ntr][ntc][nkr][nkc] = nSteps;
            Q.push( NODE( nSteps, POS( II( ntr, ntc ), II( nkr, nkc ) ) ) );
        }
    }
    
    return NONE;
}

int main() {
    while ( cin >> w >> h && w ) {
        input();
        int ret = solve();
        if ( ret == NONE ) {
            cout << "NA" << endl;
        } else {
            cout << ret << endl;
        }
    }
    return 0;
}