Go: package main

import (
	"container/heap"
	"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.Push(&pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		heap.Init(&pq)
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		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)
			}
		}
	}
	fmt.Println("NA")
}

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 <cstring>
using namespace std;

class state{
	public:
		int x1,y1,x2,y2;
		int cost;
	state(int tx,int ty,int kx,int ky,int c){
		x1 = tx;
		y1 = ty;
		x2 = kx;
		y2 = ky;
		cost = c;
	}
};
int dx1[] = {-1,1,0,0};
int dy1[] = {0,0,1,-1};
int dx2[] = {1,-1,0,0};
int dy2[] = {0,0,-1,1};

int main()
{
	int x,y;
	while(cin >> x >> y){
		if(!x&&!y)
			break;
		int tx,ty,kx,ky;
		cin >> tx >> ty;
		cin >> kx >> ky;
		bool field[52][52];
		bool memo[52][52][52][52];
		memset(field,1,sizeof(field));
		memset(memo,false,sizeof(memo));
		
		for(int i=1;i<=y;i++){
			for(int j=1;j<=x;j++){
				cin >> field[i][j];
			}
		}
		queue<state> q;
		q.push(state(tx,ty,kx,ky,0));
		memo[tx][ty][kx][ky] = true;
		int ans = -1;
		while(!q.empty()){
			state st = q.front();q.pop();
			if(st.cost >= 100)
				break;
			if(st.x1 == st.x2 && st.y1 == st.y2){
				ans = st.cost;
				break;
			}
			for(int i=0;i<4;i++){
				int nx1 = st.x1 + dx1[i];
				int ny1 = st.y1 + dy1[i];
				int nx2 = st.x2 + dx2[i];
				int ny2 = st.y2 + dy2[i];
				state nst = st;
				if(field[ny1][nx1] == 0){
					nst.x1 = nx1;
					nst.y1 = ny1;
				}
				if(field[ny2][nx2] == 0){
					nst.x2 = nx2;
					nst.y2 = ny2;
				}
				nst.cost++;
				if(memo[nst.x1][nst.y1][nst.x2][nst.y2] == false){
					memo[nst.x1][nst.y1][nst.x2][nst.y2] = true;
					q.push(nst);
				}
			}
		}
		if(ans == -1)
			cout << "NA" << endl;
		else
			cout << ans << endl;
	}
	return 0;
}

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];

bool _check(int x, int y)
{
  return x >= 0 && x < X && y >= 0 && y < Y;
}

bool check(int x1, int y1, int x2, int y2)
{
  return _check(x1, y1) && _check(x2, y2);
}

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];

      if(check(tx1, ty1, tx2, ty2) && mem[ty1][tx1] && !mem[ty2][tx2])
      {
        tx1 = x1;
        ty1 = y1;
      }
      if(check(tx1, ty1, tx2, ty2) && mem[ty2][tx2] && !mem[ty1][tx1])
      {
        tx2 = x2;
        ty2 = y2;
      }
      if(!check(tx1, ty1, tx2, ty2) || 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 <iostream>
#include <fstream>
#include <algorithm>
#include <cassert>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;

#define INF 1e9
#define rep(i,n) for(int i=0;i<n;i++)

struct C{
	int tx,ty,kx,ky;
	C(int tx,int ty,int kx,int ky):
	tx(tx),ty(ty),kx(kx),ky(ky) {}
};

int X,Y,tx,ty,kx,ky,m[51][51],dx[]={1,0,-1,0},dy[]={0,1,0,-1},d[51][51][51][51];

int bfs(int tx,int ty,int kx,int ky){
	queue<C> q;
	rep(i,Y)rep(j,X)rep(k,Y)rep(l,X)d[i][j][k][l]=INF;
	q.push(C(tx,ty,kx,ky));
	d[tx][ty][kx][ky]=0;
	while(!q.empty()){
		C c=q.front();q.pop();
		if(d[c.tx][c.ty][c.kx][c.ky]==101)return -1;
		if(c.tx==c.kx&&c.ty==c.ky)return d[c.tx][c.ty][c.kx][c.ky];
		rep(i,4){
			int ntx=c.tx+dx[i],nty=c.ty+dy[i],nkx=c.kx-dx[i],nky=c.ky-dy[i];
			if(ntx<0||ntx>=X||nty<0||nty>=Y||m[nty][ntx]){ntx=c.tx;nty=c.ty;}
			if(nkx<0||nkx>=X||nky<0||nky>=Y||m[nky][nkx]){nkx=c.kx;nky=c.ky;}
			if(d[ntx][nty][nkx][nky]==INF){
				q.push(C(ntx,nty,nkx,nky));
				d[ntx][nty][nkx][nky]=d[c.tx][c.ty][c.kx][c.ky]+1;
			}
		}
	}
	return -1;
}

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