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<set>
#include<queue>
#include<cstdio>
#define FOR(x,s,g) for(int x=(s);x<(g);x++)
using namespace std;

typedef struct{
  int x;
  int y;
} POSITION;

typedef struct{
  POSITION a;
  POSITION b;
  int depth;
} position;

bool operator<(POSITION xx,POSITION yy){
  if(xx.x < yy.x) return true;
  else if(xx.x > yy.x) return false;
  else{
    if(xx.y < yy.y) return true;
    else return false;
  } 
}

bool operator>(POSITION xx,POSITION yy){
  if(xx.x > yy.x) return true;
  else if(xx.x < yy.x) return false;
  else{
    if(xx.y > yy.y) return true;
    else return false;
  } 
}

bool operator==(POSITION a,POSITION b){
  return (a.x==b.x && a.y==b.y);
}

bool operator<(position x,position y){
  if(x.a < y.a) return true;
  else if(x.a > y.a) return false;
  else{
    if(x.b < y.b) return true;
    else return false;
  }
}

bool operator>(position x,position y){
  if(x.a > y.a) return true;
  else if(x.a < y.a) return false;
  else{
    if(x.b > y.b) return true;
    else return false;
  }
}

bool operator==(position x,position y){
  return (x.a==y.a && x.b==y.b);
}

class Map{
  bool m[50][50];
  int xsize,ysize; //mapサイズ
public:
  Map(int x,int y):xsize(x),ysize(y){
    FOR(i,0,50){
      FOR(j,0,50){
	m[i][j]=false; //non
      }
    }
  }

  void setmap(int i,int j,int s){
    m[i][j]=s;
  }

  void solve(int _ax,int _ay,int _bx,int _by){
    position p;
    p.a.x = _ax;
    p.a.y = _ay;
    p.b.x = _bx;
    p.b.y = _by;
    queue<position> q;
    p.depth=0;
    set<position> s;
    q.push(p);
    //   cout<<"start"<<endl;

    while(!q.empty()){
      p=q.front();
      q.pop();
      s.insert(p);
      //      cout<<"loop "<<p.depth<<endl;
      if(p.depth>=100){
	cout<<"NA"<<endl;
	return;
      }
      position pp=p;
      //move

      //a -> down b->up
      pp.a.y--;
      if(pp.a.y < 0 || m[pp.a.x][pp.a.y]) pp.a.y=p.a.y;
      pp.b.y++;
      if(pp.b.y >= ysize || m[pp.b.x][pp.b.y]) pp.b.y=p.b.y;
      pp.depth++;
      if(pp.a==pp.b){
	cout<<pp.depth<<endl;
	return; 
      }
      if(s.find(pp)==s.end()){
	q.push(pp);
	//	cout<<"push1"<<endl;
      }
      pp=p;

      //a -> up b->down
      pp.a.y++;
      if(pp.a.y >= ysize || m[pp.a.x][pp.a.y]) pp.a.y=p.a.y;
      pp.b.y--;
      if(pp.b.y < 0 || m[pp.b.x][pp.b.y]) pp.b.y=p.b.y;
      pp.depth++;
      if(pp.a==pp.b){
	cout<<pp.depth<<endl;
	return; 
      }
      if(s.find(pp)==s.end()){
	q.push(pp);
	//	cout<<"push2"<<endl;
      }
      pp=p;

      //a -> left b->right
      pp.a.x++;
      if(pp.a.x >=xsize || m[pp.a.x][pp.a.y]) pp.a.x=p.a.x;
      pp.b.x--;
      if(pp.b.x < 0 || m[pp.b.x][pp.b.y]) pp.b.x=p.b.x;
      pp.depth++;
      if(pp.a==pp.b){
	cout<<pp.depth<<endl;
	return; 
      }
      if(s.find(pp)==s.end()){
	q.push(pp);
	//	cout<<"push3"<<endl;
      }
      pp=p;

      //a -> right b->left
      pp.a.x--;
      if(pp.a.x < 0 || m[pp.a.x][pp.a.y]) pp.a.x=p.a.x;
      pp.b.x++;
      if(pp.b.x >=xsize || m[pp.b.x][pp.b.y]) pp.b.x=p.b.x;
      pp.depth++;
      if(pp.a==pp.b){
	cout<<pp.depth<<endl;
	return; 
      }
      if(s.find(pp)==s.end()){
	q.push(pp);
	//cout<<"push4"<<endl;
      }


    }
    cout<<"NA"<<endl;
  }

};

int main(){
  int x,y;
  while(scanf("%d %d",&x,&y) , x||y){
    int ax,ay,bx,by;
    Map m(x,y);
    cin>>ax>>ay;
    cin>>bx>>by;
    FOR(i,0,x){
      FOR(j,0,y){
	int status=0;
	cin>>status;
	m.setmap(i,j,status);
      }
    }
    m.solve(ax-1,ay-1,bx-1,by-1);
  }
  return 0;
}