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 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)
	pq = append(pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]int64, 0)
	ans := int64(102)
	for len(pq) > 0 {
		now := &Status{}
		*now = *pq[0]
		pq = pq[1:]
		if ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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++
			if next.Turn <= 100 {
				pq = append(pq, next)
			}
		}
	}
	if ans == 102 {
		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<iostream>
#include<algorithm>
#include<queue>
using namespace std;
struct Data{
	int x1,y1,x2,y2,cnt;
	Data(){}
	Data(int x1,int y1,int x2,int y2,int cnt):
		x1(x1),y1(y1),x2(x2),y2(y2),cnt(cnt){}
};
bool memo[50][50][50][50];
int dx[] = {0,1,-1,0}, dy[] = {1,0,0,-1};
int main() {
	int x,y;
	while(scanf("%d%d",&x,&y),(x|y)) {
		int tx,ty;
		int kx,ky;
		scanf("%d%d",&tx,&ty);
		scanf("%d%d",&kx,&ky);
		tx--;ty--;kx--;ky--;
		int stage[51][51];
		for(int i = 0; i < y; i++) {
			for(int j = 0; j < x; j++) {
				scanf("%d",&stage[i][j]);
			}
		}
		memset(memo,0,sizeof(memo));
		queue<Data> Q;
		Q.push(Data(tx,ty,kx,ky,0));
		int ans = -1;
		while(!Q.empty()) {
			Data d = Q.front();Q.pop();
			if(d.cnt >= 100) break;
			if(d.x1 == d.x2 && d.y1 == d.y2) {
				ans = d.cnt;
				break;
			}
			if(memo[d.x1][d.y1][d.x2][d.y2]) continue;
			memo[d.x1][d.y1][d.x2][d.y2] = true;
			for(int i = 0; i < 4; i++) {
				bool flg1 = false,flg2 = false;
				int nx1 = dx[i] + d.x1, ny1 = dy[i] + d.y1;
				int nx2 = dx[3-i] + d.x2, ny2 = dy[3-i] + d.y2;
				if(nx1 < 0 || nx1 >= x || ny1 < 0 || ny1 >= y || stage[ny1][nx1] == 1) flg1 = true;
				if(nx2 < 0 || nx2 >= x || ny2 < 0 || ny2 >= y || stage[ny2][nx2] == 1) flg2 = true;
				if(!(flg1 | flg2)) {
					Q.push(Data(nx1,ny1,nx2,ny2,d.cnt + 1));
				}
				if(!flg1 && flg2) {
					Q.push(Data(nx1,ny1,d.x2,d.y2,d.cnt+1));
				}
				if(flg1 && !flg2) {
					Q.push(Data(d.x1,d.y1,nx2,ny2,d.cnt+1));
				}
			}
		}
		if(ans == -1) puts("NA");
		else printf("%d\n",ans);
	}
	return 0;
}

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;
}