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++: #include<cstdio>
#include<cstring>
#include<map>
#include<queue>
#include<algorithm>
using namespace std;
#define INF 4000
typedef pair<int,int> p;
int xs[] = {0, 1, 0, -1}, ys[] = {1, 0, -1, 0};
int x, y;
int field[55][55];
bool dp[55][55][55][55];

int main(){
  int tx, ty, kx, ky;
  while(true){
    scanf("%d%d", &x, &y);
    memset(dp, false, sizeof(dp));
    memset(field, -1, sizeof(field));
    if(x == 0 && y == 0) return 0;
    scanf("%d%d", &tx, &ty);
    scanf("%d%d", &kx, &ky);
    for(int i = 1;i <= y;i++){
      for(int j = 1;j <= x;j++){
	scanf("%d", &field[j][i]);
      }
    }
    int ans = 0;
    bool fin = false;
    queue<pair<p, p> > q;
    q.push(make_pair(p(tx, ty), p(kx, ky)));
    dp[tx][ty][kx][ky] = true;
    while(!q.empty() && !fin && ans < 105){
      int len = q.size();
      ans++;
      while(len-- && !fin){
	pair<p, p> tmp;
	tmp = q.front();
	q.pop();
	for(int i = 0;i < 4;i++){
	  tx = tmp.first.first + xs[i];
	  ty = tmp.first.second + ys[i];
	  kx = tmp.second.first - xs[i];
	  ky = tmp.second.second - ys[i];
	  if(field[tx][ty] != 0){
	    tx = tmp.first.first;
	    ty = tmp.first.second;
	  }
	  if(field[kx][ky] != 0){
	    kx = tmp.second.first;
	    ky = tmp.second.second;
	  }
	  if(dp[tx][ty][kx][ky])continue;
	  dp[tx][ty][kx][ky] = true;
	  q.push(make_pair(p(tx, ty), p(kx, ky)));
	  if(tx == kx && ty == ky){
	    fin = true;
	    break;
	  }
	}
      }
    }
    if(!fin || ans >= 100)
      puts("NA");
    else
      printf("%d\n", ans);
  }
}