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 := &Status{}
		*now = *pq[0]
		pq = pq[1:]
		if ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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>
#include <queue>
#include <map>

#define MAX_X 50
#define MAX_Y 50

using namespace std;

typedef pair<int,int> P;
typedef pair<P,P> PP;

short d[MAX_Y][MAX_X][MAX_Y][MAX_X];

int tx,ty,kx,ky,ntx,nty,nkx,nky;
int ans;

short maze[MAX_Y][MAX_X];
int Y,X;

int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};

bool bfs(){
	queue<PP> que;
	map<PP,int> mat;
	que.push(make_pair(make_pair(ty,tx),make_pair(ky,kx)));
	
	mat[que.front()]=0;
	while (que.size()) {
		PP p=que.front();
		que.pop();
		if (p.first.first==p.second.first&&p.first.second==p.second.second) {
			ans=d[p.first.first][p.first.second][p.second.first][p.second.second];
			return true;
		}
		if (d[p.first.first][p.first.second][p.second.first][p.second.second]>=100) {
			return false;
		}
		if (mat[que.front()]) {
			continue;
		}
		for (int i=0; i<4; i++) {
			ntx=p.first.second+dx[i],nty=p.first.first+dy[i],nkx=p.second.second+dx[i]*(-1),nky=p.second.first+dy[i]*(-1);
			int flag=2;
			if (!(0<=ntx&&ntx<X&&0<=nty&&nty<Y&&maze[nty][ntx]!=1)){
				flag-=1;
				ntx=p.first.second;
				nty=p.first.first;
			}
			if (!(0<=nkx&&nkx<X&&0<=nky&&nky<Y&&maze[nky][nkx]!=1)) {
				flag-=1;
				nkx=p.second.second;
				nky=p.second.first;
			}
			if (flag!=0) {
				que.push(make_pair(make_pair(nty,ntx),make_pair(nky,nkx)));
				d[nty][ntx][nky][nkx]=d[p.first.first][p.first.second][p.second.first][p.second.second]+1;
			}
			mat[que.front()] = d[nty][ntx][nky][nkx];
		}
	}
	return false;
}

int main(){
	while (cin>>X>>Y&&X&&Y) {
		cin>>tx>>ty>>kx>>ky;
		tx-=1;
		ty-=1;
		kx-=1;
		ky-=1;
		for (int i=0; i<Y; i++) {
			for (int j=0; j<X; j++) {
				cin>>maze[i][j];
			}
		}
		if(bfs()){
			cout << ans <<endl;
		}
		else {
			cout << "NA" << endl;
		}
	}
}

C++: #include<cstring>
#include<cstdlib>
#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<stack>
using namespace std;


struct S{
  S(){};
  int tx,ty,kx,ky;
};
int X,Y;
S s;
vector<vector<int>> f;

bool input(){
  f.clear();
  s=S();
  cin>>X>>Y;
  if(X==0&&Y==0)return false;
  cin>>s.tx>>s.ty;
  cin>>s.kx>>s.ky;
  //swap(s.tx,s.ty);
  //swap(s.kx,s.ky);
  vector<int> kabe;
  for(int i=0;i<X+2;i++){
    kabe.push_back(1);
  }
  f.push_back(kabe);
  for(int i=0;i<Y;i++){
    vector<int> tt;
    tt.push_back(1);
    for(int j=0;j<X;j++){
      int tmp;
      cin>>tmp;
      tt.push_back(tmp);
    }
    tt.push_back(1);
    f.push_back(tt);
  }
  f.push_back(kabe);
  return true;
}

int vx[]={0,0,1,-1};
int vy[]={1,-1,0,0};
int used[50][50][50][50];
queue<S> q;
int bfs(S pos){
  memset(used,-1,(50*50*50*50));
  q = queue<S>();
  q.push(pos);
  used[pos.tx][pos.ty][pos.kx][pos.ky]=0;
  while(!q.empty()){
    S now = q.front();q.pop();
    if(used[now.tx][now.ty][now.kx][now.ky]>=100){
      return -1;
    }
    if(now.tx==now.kx&&now.ty==now.ky){
      return used[now.tx][now.ty][now.kx][now.ky];
    }
    for(int i=0;i<4;i++){
      S tmp = now;
      bool a,b;
      if(a=(f[tmp.tx+vx[i]][tmp.ty+vy[i]]!=1)){
        tmp.tx += vx[i];
        tmp.ty += vy[i];
      }
      if(b=(f[tmp.kx-vx[i]][tmp.ky-vy[i]]!=1)){
        tmp.kx -= vx[i];
        tmp.ky -= vy[i];
      }
      if((!(a||b))||(used[tmp.tx][tmp.ty][tmp.kx][tmp.ky]!=-1)){
        continue;
      }
      used[tmp.tx][tmp.ty][tmp.kx][tmp.ky]=used[now.tx][now.ty][now.kx][now.ky]+1;
      q.push(tmp);
    }
  }
  return -1;
}

int solve(){
  return bfs(s);
}

int main(){
  while(input()){
    int ans = solve();
    if(ans>=0){
      cout<<ans<<endl;
    }else{
      cout<<"NA"<<endl;
    }
  }
}