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
		}
		if ans<=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++: //Shuncha's code???

#include "bits/stdc++.h"
 
typedef struct {
    int ax, ay, bx, by, cnt;
} TWIN_t;
 
TWIN_t queue[300000];
int head, tail;
 
void enq(TWIN_t t)
{
    queue[(tail++) % 300000] = t;
}
 
void deq(TWIN_t *t)
{
    *t = queue[(head++) % 300000];
}
 
int main(void)
{
    TWIN_t first, temp;
    int x, y, i, j, dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1}, flag;
    char map[51][51];
    static char v[51][51][51][51];
     
    while (1){
        scanf("%d %d", &x, &y);
         
        if (x + y == 0)
            break;
         
        scanf("%d %d", &first.ax, &first.ay);
        scanf("%d %d", &first.bx, &first.by);
         
        first.ax -= 1;
        first.ay -= 1;
        first.bx -= 1;
        first.by -= 1;
         
        for (i = 0; i < y; i++){

            for (j = 0; j < x; j++)
                scanf("%d", &map[i][j]);
        }

        first.cnt = temp.cnt = 0;
        head = tail = 0;
        memset(v, 0, sizeof(v));
        v[first.ay][first.ax][first.by][first.bx] = 1;
        enq(first);
		flag = 0;

        while (head != tail){
            deq(&temp);
             
            if (temp.cnt >= 100)
                break;
             
            if (temp.ax == temp.bx && temp.ay == temp.by){
                printf("%d\n", temp.cnt);
                flag = 1;
                break;
            }
             
            for (i = 0; i < 4; i++){
                first = temp;

                if (0 <= first.ax + dx[i] && first.ax + dx[i] < x && 0 <= first.ay + dy[i] && first.ay + dy[i] < y && map[first.ay + dy[i]][first.ax + dx[i]] == 0){
                    first.ax += dx[i];
                    first.ay += dy[i];
                }

                if (0 <= first.bx - dx[i] && first.bx - dx[i] < x && 0 <= first.by - dy[i] && first.by - dy[i] < y && map[first.by - dy[i]][first.bx - dx[i]] == 0){
                    first.bx -= dx[i];
                    first.by -= dy[i];
                }

                first.cnt++;

                if (!v[first.ay][first.ax][first.by][first.bx]){
                    v[first.ay][first.ax][first.by][first.bx] = 1;
                    enq(first);
                }
            }
        }
        if (!flag)
            printf("NA\n");
    }
     
    return 0;
}

C++: #include <iostream>
#include <map>
#include <queue>
#include <sstream>

using namespace std;

const int dx[] = {0, 1, 0, -1};
const int dy[] = {-1, 0, 1, 0};

class state {
public:
    int tx, ty;
    int kx, ky;
    int time;
    state(int a, int b, int c, int d, int e) {
        tx = a;
        ty = b;
        kx = c;
        ky = d;
        time = e;
    }
};

int h, w;
int grid[55][55];
int tx, ty, kx, ky;

void solve()
{
    int ans = -1;
    state s(tx, ty, kx, ky, 0);
    map<string, bool> m;
    queue<state> q;
    ostringstream oss;

    oss << tx << "," << ty << "," << kx << "," << ky;
    q.push(s);
    m[oss.str()] = true;

    while (!q.empty()) {
        state now = q.front();
        q.pop();

        if (now.time >= 10)
            break;
        if (now.tx == now.kx && now.ty == now.ky) {
            ans = now.time;
            break;
        }

        for (int i = 0; i < 4; i++) {
            int ntx = now.tx + dx[i];
            int nty = now.ty + dy[i];
            int nkx = now.kx + dx[(i + 2) % 4];
            int nky = now.ky + dy[(i + 2) % 4];

            if (ntx < 1 || ntx > w)
                ntx = now.tx;
            if (nty < 1 || nty > h)
                nty = now.ty;
            if (nkx < 1 || nkx > w)
                nkx = now.kx;
            if (nky < 1 || nky > h)
                nky = now.ky;
            if (grid[nty][ntx] == 1) {
                ntx = now.tx;
                nty = now.ty;
            }
            if (grid[nky][nkx] == 1) {
                nkx = now.kx;
                nky = now.ky;
            }
                
            oss.str("");
            oss << ntx << "," << nty << "," << nkx << "," << nky;

            if (m.count(oss.str()) != 0)
                continue;
            state next(ntx, nty, nkx, nky, now.time + 1);
            q.push(next);
            m[oss.str()] = true;
        }
    }
    if (ans == -1 || ans >= 10)
        cout << "NA" << endl;
    else
        cout << ans << endl;
}

int main()
{
    while (cin >> w >> h, w || h) {
        cin >> tx >> ty >> kx >> ky;
        for (int y = 1; y <= h; y++)
            for (int x = 1; x <= w; x++) 
                cin >> grid[y][x];
        solve();
    }

    return 0;
}