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 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 <queue>
#include <cstring>

using namespace std;
struct PointPair {
        int step;
        int tx, ty, kx, ky;
};

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

bool passed[50][50][50][50];
bool field[50][50];

int main(){
        while(true){
                memset(passed, 0, sizeof(passed));
                memset(field, 0, sizeof(field));
                int X, Y, tx, ty, kx, ky;
                cin >> X >> Y;
                if(X == 0 || Y == 0){ break; }
                cin >> tx >> ty >> kx >> ky;
                for(int i = 0; i < Y; ++i){
                        for(int j = 0; j < X; ++j){
                                int f;
                                cin >> f;
                                field[i][j] = (f != 0);
                        }
                }
                --tx; --ty; --kx; --ky;
                PointPair init = { 0, tx, ty, kx, ky };
                queue<PointPair> q;
                q.push(init);
                passed[tx][ty][kx][ky] = true;
                int answer = -1;
                while(!q.empty()){
                        PointPair p = q.front();
                        if(p.step >= 100){ break; }
                        if(p.tx == p.kx && p.ty == p.ky){
                                answer = p.step;
                                break;
                        }
                        q.pop();
                        for(int i = 0; i < 4; ++i){
                                PointPair next;
                                next.step = p.step + 1;
                                next.tx = p.tx + dx[i];
                                next.ty = p.ty + dy[i];
                                if(field[next.tx][next.ty]){
                                        next.tx = p.tx;
                                        next.ty = p.ty;
                                }else{
                                        if(next.tx < 0){ next.tx = 0; }
                                        if(next.tx >= X){ next.tx = X - 1; }
                                        if(next.ty < 0){ next.ty = 0; }
                                        if(next.ty >= Y){ next.ty = Y - 1; }
                                }
                                next.kx = p.kx - dx[i];
                                next.ky = p.ky - dy[i];
                                if(field[next.kx][next.ky]){
                                        next.kx = p.kx;
                                        next.ky = p.ky;
                                }else{
                                        if(next.kx < 0){ next.kx = 0; }
                                        if(next.kx >= X){ next.kx = X - 1; }
                                        if(next.ky < 0){ next.ky = 0; }
                                        if(next.ky >= Y){ next.ky = Y - 1; }
                                }
                                if(!passed[next.tx][next.ty][next.kx][next.ky]){
                                        passed[next.tx][next.ty][next.kx][next.ky] = true;
                                        q.push(next);
                                }
                        }
                }
                if(answer < 0){
                        cout << "NA" << endl;
                }else{
                        cout << answer << endl;
                }
        }
        return 0;
}

C++: #include<cstring>
#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<stack>
using namespace std;
struct P{
  P(){};
  P(int a,int b){
    x=a,y=b;
  }
  int x,y;
  void move(int,int);
};
struct S{
  S(){};
  S(P a,P b){
    t=a;
    k=b;
  }
  P t,k;
  void move(int);
};

P size;
S f_pos;
vector<vector<int> > f;
bool input(){
  size=P();
  f_pos=S();
  f.clear();
  cin>>size.y>>size.x;
  if(size.x==0&&size.y==0)return false;
  cin>>f_pos.t.y>>f_pos.t.x;
  cin>>f_pos.k.y>>f_pos.k.x;
  vector<int> t;
  for(int i=0;i<size.y+2;i++){
    t.push_back(1);
  }
  f.push_back(t);
  for(int i=0;i<size.x;i++){
    vector<int> tt;
    tt.push_back(1);
    for(int j=0;j<size.y;j++){
      int tmp;
      cin>>tmp;
      tt.push_back(tmp);
    }
    tt.push_back(1);
    f.push_back(tt);
  }
  f.push_back(t);
  return true;
}
int cost[60][60][60][60];
int getCost(S s){
  return cost[s.t.x][s.t.y][s.k.x][s.k.y];
}
const int vx[]={0,0,1,-1};
const int vy[]={1,-1,0,0};
void S::move(int i){
  t.move(vx[i],vy[i]);
  k.move(-vx[i],-vy[i]);
}
void P::move(int a,int b){
  if(f[x+a][y+b]!=1){
    x+=a;
    y+=b;
  }
}
int solve(){
  memset(cost,-1,(60*60*60*60));
  queue<S> q;
  q.push(f_pos);
  cost[f_pos.t.x][f_pos.t.y][f_pos.k.x][f_pos.k.y]=0;
  while(!q.empty()){
    S now = q.front();q.pop();
    for(int i=0;i<4;i++){
      S tmp = now;
      tmp.move(i);
      if(cost[tmp.t.x][tmp.t.y][tmp.k.x][tmp.k.y]!=-1)continue;

      cost[tmp.t.x][tmp.t.y][tmp.k.x][tmp.k.y] = getCost(now)+1;
      if(getCost(tmp)>=100){
        return -1;
      }else if( (tmp.t.x==tmp.k.x)&&(tmp.t.y==tmp.k.y) ){
        return cost[tmp.t.x][tmp.t.y][tmp.k.x][tmp.k.y];
      }else{
        q.push(tmp);
      }
    }
  }
  return -1;
}
int main(){
  while(input()){
    int ans= solve();
    if(ans==-1||ans>=100){
      cout<<"NA"<<endl;
    }else{
      cout<<ans<<endl;
    }
  }
}