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 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 <queue>
#include <cstring>

using namespace std;
struct PointPair {
        int step;
        int tx, ty, kx, ky;
};

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

bool passed[50][50][50][50];
bool field[50][50];

int main(){
        while(true){
                memset(passed, 0, sizeof(passed));
                memset(field, 0, sizeof(field));
                int X, Y, tx, ty, kx, ky;
                cin >> X >> Y;
                if(X == 0 || Y == 0){ break; }
                cin >> tx >> ty >> kx >> ky;
                for(int i = 0; i < Y; ++i){
                        for(int j = 0; j < X; ++j){
                                int f;
                                cin >> f;
                                field[i][j] = (f != 0);
                        }
                }
                --tx; --ty; --kx; --ky;
                PointPair init = { 0, tx, ty, kx, ky };
                queue<PointPair> q;
                q.push(init);
                passed[tx][ty][kx][ky] = true;
                int answer = -1;
                while(!q.empty()){
                        PointPair p = q.front();
                        if(p.step >= 100){ break; }
                        if(p.tx == p.kx && p.ty == p.ky){
                                answer = p.step;
                                break;
                        }
                        q.pop();
                        for(int i = 0; i < 4; ++i){
                                PointPair next;
                                next.step = p.step + 1;
                                next.tx = p.tx + dx[i];
                                next.ty = p.ty + dy[i];
                                if(field[next.tx][next.ty]){
                                        next.tx = p.tx;
                                        next.ty = p.ty;
                                }else{
                                        if(next.tx < 0){ next.tx = 0; }
                                        if(next.tx >= X){ next.tx = X - 1; }
                                        if(next.ty < 0){ next.ty = 0; }
                                        if(next.ty >= Y){ next.ty = Y - 1; }
                                }
                                next.kx = p.kx - dx[i];
                                next.ky = p.ky - dy[i];
                                if(field[next.kx][next.ky]){
                                        next.kx = p.kx;
                                        next.ky = p.ky;
                                }else{
                                        if(next.kx < 0){ next.kx = 0; }
                                        if(next.kx >= X){ next.kx = X - 1; }
                                        if(next.ky < 0){ next.ky = 0; }
                                        if(next.ky >= Y){ next.ky = Y - 1; }
                                }
                                if(!passed[next.tx][next.ty][next.kx][next.ky]){
                                        passed[next.tx][next.ty][next.kx][next.ky] = true;
                                        q.push(next);
                                }
                        }
                }
                if(answer < 0){
                        cout << "NA" << endl;
                }else{
                        cout << answer << endl;
                }
        }
        return 0;
}