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>

using namespace std;


struct P {
	int x, y;
};

struct data {
	P tp, kp;
	int step;
};

bool used[50][50][50][50] = {0};
int m[50][50];
int W, H;

P move(P p, P d) {
	P next = (P){ p.x+d.x, p.y+d.y };
	if (next.x < 0 || next.x >= W || next.y < 0 || next.y >= H) return p;
	if (m[next.y][next.x]) return p;
	return next;
}

int main() {
	while ( cin >> W >> H, W || H ) {
		int tx, ty; cin >> tx >> ty; --tx, --ty;
		int kx, ky; cin >> kx >> ky; --kx, --ky;
		for (int y = 0; y < H; ++y) {
			for (int x = 0; x < W; ++x) {
				cin >> m[y][x];
			}
		}
		fill(&used[0][0][0][0], &used[0][0][0][0]+50*50*50*50, false);
		queue<data> Q; Q.push( (data){ (P){tx, ty}, (P){kx, ky}, 0} );
		int ans = -1;
		while ( !Q.empty() ) {
			data d = Q.front(); Q.pop();
			P tp = d.tp, kp = d.kp;

			if (tp.x < 0 || tp.x >= W || tp.y < 0 || tp.y >= H) continue;
			if (kp.x < 0 || kp.x >= W || kp.y < 0 || kp.y >= H) continue;
			if (m[tp.y][tp.x]) continue;
			if (m[kp.y][kp.x]) continue;

			if (used[tp.x][tp.y][kp.x][kp.y]) continue;
			used[tp.x][tp.y][kp.x][kp.y] = true;

			if (tp.x == kp.x && tp.y == kp.y) {
				ans = d.step;
				break;
			}

			Q.push( (data){ move(tp, (P){0, 1}), move(kp, (P){0, -1}), d.step+1} );
			Q.push( (data){ move(tp, (P){0, -1}), move(kp, (P){0, 1}), d.step+1} );
			Q.push( (data){ move(tp, (P){1, 0}), move(kp, (P){-1, 0}), d.step+1} );
			Q.push( (data){ move(tp, (P){-1, 0}), move(kp, (P){1, 0}), d.step+1} );
		}
		if (ans < 0) cout << "NA" << endl;
		else cout << ans << endl;
	}
}

C++: #include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<complex>
#include<cmath>
#include<algorithm>
#include<map>
#include<vector>
#include<sstream>
#include<queue>
#include<iostream>
using namespace std;
struct data{
    int x;
    int y;
    int u;
    int v;
    int t;
};

bool vis[60][60][60][60] = {};
const int dx[] = {1,0,-1,0},dy[] = {0,1,0,-1};
int main(void){
    int w,h;
    while(cin>>w>>h,w){
        int x,y,u,v;
        cin>>x>>y>>u>>v;
        bool screen[60][60] = {};
        for(int i = 0;i < h;i++){
            for(int j = 0;j < w;j++){
                cin>>screen[i][j];
            }
        }
        data D;
        D.x = x,D.y = y;
        D.u = u,D.v = v;
        D.t = 0;
        queue<data> Q;
        Q.push(D);

        while(!Q.empty()){
            data E = Q.front();Q.pop();

            vis[E.x][E.y][E.u][E.v] = true;
            vis[E.u][E.v][E.x][E.y] =true;
            if(E.x == E.u&&E.y == E.v){
                cout<<E.t<<endl;
                goto e;
            }
            for(int i = 0;i < 4;i++){
                if(0<=E.x+dx[i]&&E.x+dx[i]<w&&0<=E.y+dy[i]&&E.y+dy[i]<h&&
                   0<=E.u+dx[(i+2)%4]&&E.u+dx[(i+2)%4]<w&&0<=E.v+dy[(i+2)%4]&&E.v+dy[(i+2)%4]<h){

                    data F = E;
                    F.t++;
                    F.x+=dx[i],F.y+=dy[i],F.u+=dx[(i+2)%4],F.v+=dy[(i+2)%4];
                    if(!vis[F.x][F.y][F.u][F.v]&&!vis[F.u][F.v][F.x][F.y]&&!screen[F.x][F.y]&&!screen[F.u][F.v]){
                        Q.push(F);
                    }
                }
            }

        }
        cout<<"NA"<<endl;
        e:;
    }


    return 0;
}

C++: #include<bits/stdc++.h>
#define INF (1e9)
#define s second
#define f first
#define N 50
using namespace std;
typedef pair<int,int> P;
typedef pair<P,P> P1;
typedef pair<int,P1> P2;
int x,y,stx,sty,skx,sky;
int d[N][N][N][N];
int dat[N][N];
int dy[4]={-1,0,1,0};
int dx[4]={0,1,0,-1};

int bfs(){
  queue<P2> q;
  d[sty][stx][sky][skx]=0;
  q.push(P2(0,P1(P(sty,stx),P(sky,skx))));
  while(!q.empty()){
    P2 t=q.front(); q.pop();
    int cost=t.f;
    int ty=t.s.f.f,tx=t.s.f.s;
    int ky=t.s.s.f,kx=t.s.s.s;
    if(d[ty][tx][ky][kx]<cost)continue;
    if(ty==ky&&tx==kx)return cost;
    for(int i=0;i<4;i++){
      int nty=ty+dy[i],ntx=tx+dx[i];
      int nky=ky-dy[i],nkx=kx-dx[i];
      if(nty<0||ntx<0||y<=nty||x<=ntx)
	nty=ty,ntx=tx;
      else if(dat[nty][ntx])
	nty=ty,ntx=tx;
      if(nky<0||nkx<0||y<=nky||x<=nkx)
	nky=ky,nkx=kx;
      else if(dat[nky][nkx])
	nky=ky,nkx=kx;
      if(d[nty][ntx][nky][nkx]>cost+1){
	d[nty][ntx][nky][nkx]=cost+1;
	q.push(P2(cost+1,P1(P(nty,ntx),P(nky,nkx))));
      }
    }
  }
  return -1;
}

int main(){
  while(1){
    cin>>x>>y;
    if(!x&&!y)break;
    cin>>stx>>sty>>skx>>sky;
    for(int i=0;i<y;i++)
      for(int j=0;j<x;j++)
	cin>>dat[i][j];
    for(int i=0;i<y;i++)
      for(int j=0;j<x;j++)
	for(int k=0;k<y;k++)
	  for(int l=0;l<x;l++)
	    d[i][j][k][l]=INF;
    int ans=bfs();
    if(ans==-1)cout<<"NA"<<endl;
    else cout<<ans<<endl;

  }
  return 0;
}