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>
using namespace std;

int x,y,tx,ty,kx,ky,cou;
int mas[111][111];
int ans=0;
bool used[111][111][111][111];
int dx[]={-1,0,0,1};
int dy[]={0,-1,1,0};
struct P{
  int tx,ty,kx,ky,cou;
  P(int tx,int ty,int kx,int ky,int cou):tx(tx),ty(ty),kx(kx),ky(ky),cou(cou){}
};
int bfs();

int main(){
  while(1){
    cin >> x >> y;
    if(x==0 && y==0) break;
    memset(used,false,sizeof(used));
    cin >> tx >> ty;
    cin >> kx >> ky;
    for(int i=0;i<y;i++){
      for(int j=0;j<x;j++){
	cin >> mas[i][j];
      }
    }
    ans = bfs();
    if(ans==-1) cout << "NA" << endl;
    else cout << ans << endl;
  }
}

int bfs(){
  queue<P> que;
  que.push(P(tx-1,ty-1,kx-1,ky-1,0));
  used[tx-1][ty-1][kx-1][ky-1] = true;
  while(!que.empty()){
    P p=que.front();
    if(p.tx==p.kx && p.ty==p.ky) return p.cou;
    else if(p.cou>=100) return -1;
    for(int i=0;i<4;i++){
      int ntx=p.tx+dx[i];
      int nty=p.ty+dy[i];
      int nkx=p.kx+dx[3-i];
      int nky=p.ky+dy[3-i];
      if(ntx<0 || ntx>=x || nty<0 || nty>=y || mas[nty][ntx]==1){
	ntx=p.tx;
	nty=p.ty;
      }
      if(nkx<0 || nkx>=x || nky<0 || nky>=y || mas[nky][nkx]==1){
	nkx=p.kx;
	nky=p.ky;
      }
      if(used[ntx][nty][nkx][nky]==false){
	que.push(P(ntx,nty,nkx,nky,p.cou+1));
	used[ntx][nty][nkx][nky] = true;
      }
    }
    que.pop();
  }
  return -1;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <time.h>
 
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef int ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<pr,pr> ppr;
typedef priority_queue<pr,Vpr, greater<pr> > PQ;
const int SIZE=1e+5 + 1;
const ut INF=1<<30;
const ld eps=1e-6;
const LL mod=1e+9 + 7;

int tdx[] = {0, 1, 0, -1}, tdy[] = {-1, 0, 1, 0};
int kdx[] = {0, -1, 0, 1}, kdy[] = {1, 0, -1, 0};

int W, H;
int maze[64][64];

typedef struct State {
	int tx, ty, kx, ky, d;
	State(int tx, int ty, int kx, int ky, int d) : tx(tx), ty(ty), kx(kx), ky(ky), d(d){}
	
	bool operator < (const State s) const {
		if(tx != s.tx) return tx < s.tx;
		if(ty != s.ty) return ty < s.ty;
		if(kx != s.kx) return kx < s.kx;
		if(ky != s.ky) return ky < s.ky;
		return false;
	}
} State;

bool check(int x, int y){
	return x >= 0 && x < W && y >= 0 && y < H && maze[y][x] == 0;	
}

int main() {
	while(cin >> W >> H && W){
		int tx, ty, kx, ky;
		memset(maze, 0, sizeof(maze));
		cin >> tx >> ty >> kx >> ky;
		tx--; ty--; kx--; ky--;
		REP(i,H)REP(j,W)
			scanf("%d", &maze[i][j]);
			
		queue<State> que;
		que.push(State(tx, ty, kx, ky, 0));
		map<State, bool> visited;
		bool ok = false;
		while(!que.empty()){
			State s = que.front(); que.pop();
			if(s.d >= 100)
				continue;
			if(s.tx == s.kx && s.ty == s.ky){
				cout << s.d << endl;
				ok = true;
				break;
			}
			REP(i,4){
				int ntx = s.tx + tdx[i], nty = s.ty + tdy[i];
				int nkx = s.kx + kdx[i], nky = s.ky + kdy[i];
				if(!check(ntx, nty)){
					ntx = s.tx;
					nty = s.ty;
				}
				if(!check(nkx, nky)){
					nkx = s.kx;
					nky = s.ky;
				}
				State nState = State(ntx, nty, nkx, nky, 0);
				if(!visited[nState]){
					visited[nState] = true;
					nState.d = s.d + 1;
					que.push(nState);
				}
			}
		}
		if(!ok)
			cout << "NA" << endl;
	}
  return 0;
}