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

bool d[50][50][50][50];
int X, Y, tx, ty, kx, ky;
int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0}, mem[50][50];
int main()
{
loop:
  cin >> X >> Y;
  if(!X)
    return 0;
  cin >> tx >> ty >> kx >> ky;
  tx--; ty--; kx--; ky--;
  for(int y = 0; y < Y; y++)
  {
    for(int x = 0; x < X; x++)
    {
      int a;
      cin >> a;
      mem[y][x] = a;
    }
  }

  fill_n((bool*)d, 50 * 50 * 50 * 50, 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)
    {
      cout << "NA" << endl;
      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];

      bool b1 = ty1 < 0 || ty1 >= Y || tx1 < 0 || tx1 >= X || mem[ty1][tx1] == 1;
      bool b2 = ty2 < 0 || ty2 >= Y || tx2 < 0 || tx2 >= X || mem[ty2][tx2] == 1;

      if(b1)
      {
        tx1 = x1;
        ty1 = y1;
      }
      if(b2)
      {
        tx2 = x2;
        ty2 = y2;
      }
      if(d[tx1][ty1][tx2][ty2])
        continue; 

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

C++: #include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstring>
#include <sstream>
#include <cassert>
#include <list>
using namespace std;
static const double EPS = 1e-8;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> PI;
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
#define mp(a,b) make_pair(a,b)
#define pb(a) push_back(a)
#define SZ(a) (int(a.size()))
#define F first
#define S second
const double pi=acos(-1);
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};

int X,Y,tx,ty,kx,ky;
int wall[50][50];
bool vis[50][50][50][50];

typedef struct _node{
  int cost,tx,ty,kx,ky;
  int geth()const{
    return (abs(tx-kx)+abs(ty-ky))/2;
  }
  bool operator<(const _node& r)const{
    return cost+geth()>r.cost+r.geth();
  }
  _node (int c,int atx,int aty,int akx,int aky){
    cost=c;
    tx=atx;
    ty=aty;
    kx=akx;
    ky=aky;
  }
}node;

void solve(){
  cin>>tx>>ty>>kx>>ky;
  rep(i,Y)rep(j,X)cin>>wall[i][j];

  priority_queue<node>q;
  q.push(node(0,tx,ty,kx,ky));
  memset(vis,0,sizeof(vis));
  while(!q.empty()){
    int cc=q.top().cost;
    tx=q.top().tx;
    ty=q.top().ty;
    kx=q.top().kx;
    ky=q.top().ky;
    q.pop();
    if(cc>=100 || vis[tx][ty][kx][ky])continue;
    vis[tx][ty][kx][ky]=true;
    if(tx==kx && ty==ky){
      cout<<cc<<endl;
      return;
    }
    rep(i,4){
      int ntx=tx+dx[i],nty=ty+dy[i];
      int nkx=kx-dx[i],nky=ky-dy[i];

      if(0>ntx || ntx>=X ||
         0>nty || nty>=Y ||
         wall[nty][ntx])ntx=tx,nty=ty;
      if(0>nkx || nkx>=X ||
         0>nky || nky>=Y ||
         wall[nky][nkx])nkx=kx,nky=ky;
      if(vis[ntx][nty][nkx][nky])continue;
      q.push(node(cc+1,ntx,nty,nkx,nky));
    }
  }
  cout<<"NA"<<endl;
}

main(){
  while(cin>>X>>Y,X)
    solve();
}