Go: package main

import (
	"container/heap"
	"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.Push(&pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		heap.Init(&pq)
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		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)
			}
		}
	}
	fmt.Println("NA")
}

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 <string>
#include <queue>
using namespace std;

struct Point{
  int tx,ty,kx,ky,time;
};

int main(){
  int i,j,k,l,X,Y;
  bool G[51][51],D[5151][5151];
  while(1){
    Point p;
    queue <Point> Q;
    cin >> X >> Y;
    if(X == 0 && Y == 0) break;
    cin >> p.tx >> p.ty;
    cin >> p.kx >> p.ky;

    l = 100;
    for(i=1;i<=Y;i++){
      for(j=1;j<=X;j++){
	cin >> G[j][i];
	D[j][i] = 0;
	for(k=100;k<=100*X;k++) D[k+j][l+i] = false;
      }
      i += 100;
    }

    Q.push(p);
    D[p.tx][p.ty] = 0;
    p.time = 0;

    while(!Q.empty()){
      p = Q.front();
      Q.pop();
      if(p.tx == p.kx && p.ty == p.ky || p.time >= 100) break;
      int x[4] = {1,0,-1,0};
      int y[4] = {0,1,0,-1};
      Point v;

      for(i=0;i<4;i++){
	int ntx = p.tx + x[i];
	int nty = p.ty + y[i];
	int nkx = p.kx + x[(i+2)%4];
	int nky = p.ky + y[(i+2)%4];
	if(ntx > 1 && nkx > 1 && ntx <= X && nkx <= X && nty > 1 && nky > 1 && nty <= Y && nky <= Y && !D[ntx+100*nkx][nty+100*nky] && !G[ntx][nty] && !G[nkx][nky]){
	  D[ntx+100*nkx][nty+100*nky] = true;
	  v.tx = ntx;
	  v.ty = nty;
	  v.kx = nkx;
	  v.ky = nky;
	  v.time = p.time + 1;
	  Q.push(v);
	}
	else if(nkx > 1 && nkx <= X && nky > 1 && nky <= Y && !G[nkx][nky] && (ntx < 1 || ntx > X || nty < 1 || nty > Y || G[ntx][nty]) && !D[p.tx+100*nkx][p.ty+100*nky]){
	  D[p.tx+100*nkx][p.ty+100*nky] = true;
	  v.tx = p.tx;
	  v.ty = p.ty;
	  v.kx = nkx;
	  v.ky = nky;
	  v.time = p.time + 1;
	  Q.push(v);
	}
	else if(ntx > 1 && ntx <= X && nty > 1 && nty <= Y && !G[ntx][nty] && (nkx < 1 || nkx > X || nky < 1 || nky > Y || G[nkx][nky]) && !D[ntx+100*p.kx][nty+100*p.ky]){
	  D[ntx+100*p.kx][nty+100*p.ky] = true;
	  v.tx = ntx;
	  v.ty = nty;
	  v.kx = p.kx;
	  v.ky = p.ky;
	  v.time = p.time + 1;
	  Q.push(v);
	}
      }
    }

    if(p.time < 100) cout << p.time << endl;
    else cout << "NA" << endl;
    
  }
  return 0;
}

C++: /*

	??????????£???§??????????????´?????????????????????
	???????????±???????±???????????????????????????¢

	??????????????§break ??§???????????????
	 <-------- ????????¢

	 TIME LIMITED
*/

#include <iostream>
using namespace std;
#include<queue>
#include<cstring>

int flg[51][51][51][51];

struct Twins
{
	int tax, tay;
	int kax, kay;
	int cnt;
};

queue <Twins> que;

bool check(int y1, int x1, int y2, int x2){ //?????§????????£?????¢?´¢??????


	if (flg[y1][x1][y2][x2] == 0) return true;
	return false;
}

int main(void){

	int x, y;
	int tx, ty;
	int kx, ky;
	Twins twins;

	int y_temp[4] = { -1, +1, 0, 0 };//????????????
	int x_temp[4] = { 0, 0, -1, +1 };//????????????

	while (cin >> x >> y && x != 0 && y != 0){

		memset(flg, 0, sizeof(flg));

		while (!que.empty())
			que.pop();
		int map[52][52];
		memset(map, 1, sizeof(map));

		cin >> tx >> ty >> kx >> ky;

		twins.cnt = 0, twins.tax = tx, twins.tay = ty, twins.kax = kx, twins.kay = ky;

		for (int i = 1; i < y + 1; i++){
			for (int j = 1; j < x + 1; j++)
					cin >> map[i][j];
		}

		que.push(twins);
		flg[que.front().tay][que.front().tax][que.front().kay][que.front().kax] = 1;

		while (1){

			if (que.front().cnt >= 100){
				break;
			}
			if (que.front().kax == que.front().tax && que.front().kay == que.front().tay){
				break;
			}

			for (int i = 0; i < 4; i++){
				if (map[que.front().tay + y_temp[i]][que.front().tax + x_temp[i]] == 0){ //T???????????????????£???????
					if (map[que.front().kay - y_temp[i]][que.front().kax - x_temp[i]] == 0){ //K???????????????????£???????
						if (check(que.front().tay + y_temp[i], que.front().tax + x_temp[i], que.front().kay - y_temp[i], que.front().kax - x_temp[i])){
							twins.tay = que.front().tay + y_temp[i], twins.tax = que.front().tax + x_temp[i], twins.kay = que.front().kay -y_temp[i], twins.kax = que.front().kax - x_temp[i];
							twins.cnt = que.front().cnt + 1;
							que.push(twins);
							flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
						}
					}
					else if (check(que.front().tay + y_temp[i], que.front().tax + x_temp[i], que.front().kay, que.front().kax)){
						twins.tay = que.front().tay + y_temp[i], twins.tax = que.front().tax + x_temp[i], twins.kay = que.front().kay, twins.kax = que.front().kax;
						twins.cnt = que.front().cnt + 1;
						que.push(twins);
						flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
					}
				}
				else if (map[que.front().kay - y_temp[i]][que.front().kax - x_temp[i]] == 0){ //K???????????????????£???????
					if (check(que.front().tay, que.front().tax, que.front().kay - y_temp[i], que.front().kax - x_temp[i])){
						twins.tay = que.front().tay, twins.tax = que.front().tax, twins.kay = que.front().kay - y_temp[i], twins.kax = que.front().kax - x_temp[i];
						twins.cnt = que.front().cnt + 1;
						que.push(twins);
						flg[twins.tay][twins.tax][twins.kay][twins.kax] = 1;
					}
				}
			}

			que.pop();
			if (que.empty())
				break;
		}

		if (que.empty() || que.front().cnt >= 100)
			cout << "NA" << endl;
		else
			cout << que.front().cnt << endl;

	}
}