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 <queue>

typedef std::pair<int, int> P; //(x,y)
typedef std::pair<P, P> PP;
typedef std::pair<PP, int> D;

int x, y;
int map[51][51];
bool visit[51][51][51][51];

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

bool back(P p){
	if(map[p.second][p.first])return true;
	else if(p.second < 0 || p.second >= y || p.first < 0 || p.first >= x)return true;
	else return false;
}

int main(){
	while(true){
		for(int i = 0; i < 51; ++i)for(int j = 0; j < 51; ++j)for(int k = 0; k < 51; ++k)for(int l = 0; l < 51; ++l)visit[i][j][k][l] = false;
		
		std::cin >> x >> y;
		if(x == 0 && y == 0)break;
		
		P t, k;
		std::cin >> t.first >> t.second;
		std::cin >> k.first >> k.second;
		--t.first, --t.second;
		--k.first, --k.second;

		for(int i = 0; i < y; ++i){
			for(int j = 0; j < x; ++j){
				std::cin >> map[i][j];
			}
		}

		bool f = false;

		std::queue<D> que;
		que.push(D(PP(t, k), 0));
		
		visit[t.first][t.second][k.first][k.second] = true;

		while(!que.empty()){
			D d = que.front();
			que.pop();
			
			P ct = d.first.first, ck = d.first.second;
			
			if(d.second >= 100){
				break;
			}
			if(ct == ck){
				f = true;
				std::cout << d.second << std::endl;
				break;
			}
			
			for(int i = 0; i < 4; ++i){
				P nt = ct, nk = ck;
				nt.first += dx[i]; nt.second += dy[i];
				nk.first -= dx[i]; nk.second -= dy[i];
				
				if(back(nt))nt = ct;
				if(back(nk))nk = ck;
				
				if(!visit[nt.first][nt.second][nk.first][nk.second]){
					visit[nt.first][nt.second][nk.first][nk.second] = true;	
					que.push(D(PP(nt, nk), d.second + 1));
				}
			}
		}
		
		if(!f)std::cout << "NA" << std::endl;
	}
	return 0;
}