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 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)
	pq = append(pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]int64, 0)
	ans := int64(102)
	for len(pq) > 0 {
		now := pq[0]
		pq = pq[1:]
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if ans <= now.Turn {
			continue
		}

		if _, ok := memo[now.Person]; ok {
			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++
			if next.Turn <= 100 {
				pq = append(pq, next)
			}
		}
	}
	if ans == 102 {
		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>
#define M 52
#include<queue>
#include<cstring>
using namespace std;
struct P{
	int ax,ay,bx,by,cost;
	P(){}
	P(int h,int j,int k,int l,int co):
	ax(h),ay(j),bx(k),by(l),cost(co){}
	
};
int main(){
	bool s[M][M],d[M][M][M][M],u;
	int w,h,tx,ty,kx,ky,dx[]={1,-1,0,0},dy[]={0,0,-1,1};
	while(cin>>w>>h,w||h){
		cin>>tx>>ty;tx--;ty--;
		cin>>kx>>ky;kx--;ky--;
		for(int i=0;i<h;i++)
		for(int j=0;j<w;j++)
		cin>>s[i][j];
		queue<P> que;
		memset(d,sizeof(d),0);
		d[tx][ty][kx][ky]=1;
		que.push(P(tx,ty,kx,ky,0));
		u=true;
		while(!que.empty()){
			P p=que.front();
			que.pop();
			if(p.cost==100)
			break;
			if(p.ax==p.bx&&p.ay==p.by){
				cout<<p.cost<<endl;
				u=false;
				break;
			}
			int ntx,nty,nkx,nky;
			for(int i=0;i<4;i++){
				ntx=p.ax+dx[i];
				nty=p.ay+dy[i];
				nkx=p.bx-dx[i];
				nky=p.by-dy[i];
				if(!(ntx>=0&&ntx<w&&nty>=0&&nty<h)||s[nty][ntx]==1){
					ntx=tx;nty=ty;
				}
				if(!(nkx>=0&&nkx<w&&nky>=0&&nky<h)||s[nky][nkx]==1){
					nkx=kx;nky=ky;
				}
				if(d[ntx][nty][nkx][nky]!=1)
				que.push(P(ntx,nty,nkx,nky,p.cost+1));
				d[ntx][nty][nkx][nky]=1;
			}
		}
		if(u)
		cout<<"NA"<<endl;
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<queue>
using namespace std;

bool d[52][52][52][52];
int X, Y, tx, ty, kx, ky;
int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0}, mem[52][52];

int main()
{
loop:
  cin >> X >> Y;
  if(!X)
    return 0;
  cin >> tx >> ty >> kx >> ky;
  for(int y = 1; y <= Y; y++)
  {
    for(int x = 1; x <= X; x++)
    {
      int a;
      cin >> a;
      mem[y][x] = a;
    }
    mem[y][0] = 1;
    mem[y][X + 1] = 1;
  }
  for(int x = 0; x <= X + 1; x++)
  {
    mem[0][x] = 1;
    mem[Y + 1][x] = 1;
  }

  fill_n((bool*)d, 52 * 52 * 52 * 52, false);
  
  queue<int> q;
  q.push(tx);
  q.push(ty);
  q.push(kx);
  q.push(ky);
  q.push(0);
  while(!q.empty())
  {
    int x1 = q.front(); q.pop();
    int y1 = q.front(); q.pop();
    int x2 = q.front(); q.pop();
    int y2 = q.front(); q.pop();
    int n = q.front(); q.pop();
    
    if(n > 100)
    {
      break;
    }
    
    if(y1 == y2 && x1 == x2)
    {
      cout << n << endl;
      goto loop;
    }

    for(int i = 0; i < 4; i++)
    {
      int tx1 = x1 + dx[i];
      int ty1 = y1 + dy[i];
      int tx2 = x2 - dx[i];
      int ty2 = y2 - dy[i];

      if(mem[ty1][tx1])
      {
        tx1 = x1;
        ty1 = y1;
      }
      if(mem[ty2][tx2])
      {
        tx2 = x2;
        ty2 = y2;
      }
      if(d[tx1][ty1][tx2][ty2])
        continue; 

      d[tx1][ty1][tx2][ty2] = true;
      q.push(tx1);
      q.push(ty1);
      q.push(tx2);
      q.push(ty2);
      q.push(n + 1);
    }
  }
  cout << "NA" << endl;
  goto loop;
}

C++: #include<cstring>
#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<stack>
using namespace std;
struct P{
  P(){};
  P(int a,int b){
    x=a,y=b;
  }
  int x,y;
  void move(int,int);
};
struct S{
  S(){};
  S(P a,P b){
    t=a;
    k=b;
  }
  P t,k;
  void move(int);
};
 
P size;
S f_pos;
vector<vector<int> > f;
bool input(){
  size=P();
  f_pos=S();
  f.clear();
  cin>>size.y>>size.x;
  if(size.x==0&&size.y==0)return false;
  cin>>f_pos.t.y>>f_pos.t.x;
  cin>>f_pos.k.y>>f_pos.k.x;
  vector<int> t;
  for(int i=0;i<size.y+2;i++){
    t.push_back(1);
  }
  f.push_back(t);
  for(int i=0;i<size.x;i++){
    vector<int> tt;
    tt.push_back(1);
    for(int j=0;j<size.y;j++){
      int tmp;
      cin>>tmp;
      tt.push_back(tmp);
    }
    tt.push_back(1);
    f.push_back(tt);
  }
  f.push_back(t);
  return true;
}
int cost[60][60][60][60];
const int vx[]={0,0,1,-1};
const int vy[]={1,-1,0,0};
void S::move(int i){
  t.move(vx[i],vy[i]);
  k.move(-vx[i],-vy[i]);
}
void P::move(int a,int b){
  if(f[x+a][y+b]!=1){
    x+=a;
    y+=b;
  }
}
int solve(){
  memset(cost,-1,sizeof(cost));
  queue<S> q;
  q.push(f_pos);
  cost[f_pos.t.x][f_pos.t.y][f_pos.k.x][f_pos.k.y]=0;
  while(!q.empty()){
    S now = q.front();q.pop();
    for(int i=0;i<4;i++){
      S tmp = now;
      tmp.move(i);
      if(cost[tmp.t.x][tmp.t.y][tmp.k.x][tmp.k.y]!=-1)continue;
 
      cost[tmp.t.x][tmp.t.y][tmp.k.x][tmp.k.y] = cost[now.t.x][now.t.y][now.k.x][now.k.y]+1;
      if(cost[tmp.t.x][tmp.t.y][tmp.k.x][tmp.k.y]>=100){
        return -1;
      }else if( (tmp.t.x==tmp.k.x)&&(tmp.t.y==tmp.k.y) ){
        return cost[tmp.t.x][tmp.t.y][tmp.k.x][tmp.k.y];
      }else{
        q.push(tmp);
      }
    }
  }
  return -1;
}
int main(){
  while(input()){
    /*
    for(int i=0;i<f.size();i++){
      for(int j=0;j<f[i].size();j++){
        cout<<f[i][j];
      }cout<<endl;
    }cout<<endl;
    */
    int ans= solve();
    if(ans==-1||ans>=100){
      cout<<"NA"<<endl;
    }else{
      cout<<ans<<endl;
    }
  }
}