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<cstring>
#include<cstdlib>
#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<stack>
using namespace std;


struct S{
  S(){};
  int tx,ty,kx,ky;
};
int X,Y;
S s;
vector<vector<int> > f;

bool input(){
  f.clear();
  s=S();
  cin>>X>>Y;
  if(X==0&&Y==0)return false;
  cin>>s.tx>>s.ty;
  cin>>s.kx>>s.ky;
  swap(s.tx,s.ty);
  swap(s.kx,s.ky);
  vector<int> kabe;
  for(int i=0;i<X+2;i++){
    kabe.push_back(1);
  }
  f.push_back(kabe);
  for(int i=0;i<Y;i++){
    vector<int> tt;
    tt.push_back(1);
    for(int j=0;j<X;j++){
      int tmp;
      cin>>tmp;
      tt.push_back(tmp);
    }
    tt.push_back(1);
    f.push_back(tt);
  }
  f.push_back(kabe);
  return true;
}

int vx[]={0,0,1,-1};
int vy[]={1,-1,0,0};
int used[60][60][60][60];
queue<S> q;
int bfs(S pos){
  memset(used,-1,(60*60*60*60));
  q = queue<S>();
  q.push(pos);
  used[pos.tx][pos.ty][pos.kx][pos.ky]=0;
  while(!q.empty()){
    S now = q.front();q.pop();
    if(used[now.tx][now.ty][now.kx][now.ky]>=100){
      return -1;
    }
    if(now.tx==now.kx&&now.ty==now.ky){
      return used[now.tx][now.ty][now.kx][now.ky];
    }
    for(int i=0;i<4;i++){
      S tmp = now;
      bool a,b;
      if(a=(f[tmp.tx+vx[i]][tmp.ty+vy[i]]!=1)){
        tmp.tx += vx[i];
        tmp.ty += vy[i];
      }
      if(b=(f[tmp.kx-vx[i]][tmp.ky-vy[i]]!=1)){
        tmp.kx -= vx[i];
        tmp.ky -= vy[i];
      }
      if((!(a||b))||(used[tmp.tx][tmp.ty][tmp.kx][tmp.ky]!=-1)){
        continue;
      }
      used[tmp.tx][tmp.ty][tmp.kx][tmp.ky]=used[now.tx][now.ty][now.kx][now.ky]+1;
      q.push(tmp);
    }
  }
  return -1;
}

int solve(){
  return bfs(s);
}

int main(){
  while(input()){
    int ans = solve();
    if(ans>=0){
      cout<<ans<<endl;
    }else{
      cout<<"NA"<<endl;
    }
  }
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <cstring>
#include <queue>
using namespace std;

int X, Y;
int field[50][50];

bool visit[50][50][50][50];

struct Node {
	int takx, taky;
	int kazx, kazy;
	int turn;
	Node(int takx, int taky, int kazx, int kazy) : takx(takx), taky(taky), kazx(kazx), kazy(kazy), turn(0) {}

	bool isOk() {
		return takx == kazx && taky == kazy;
	}

	// right, up, left, down
	Node move(int dir) {
		static int dx[4] = {1, 0, -1, 0};
		static int dy[4] = {0, 1, 0, -1};
		Node next = *this;

		int nx, ny;

		nx = takx + dx[dir];
		ny = taky + dy[dir];

		if(0 <= nx && nx < X && 0 <= ny && ny < Y) {
			if(field[nx][ny] == 0) next.takx = nx, next.taky = ny;
		}

		nx = kazx + dx[(dir + 2) % 4];
		ny = kazy + dy[(dir + 2) % 4];

		if(0 <= nx && nx < X && 0 <= ny && ny < Y) {
			if(field[nx][ny] == 0) next.kazx = nx, next.kazy = ny;
		}

		next.turn++;
		return next;
	}
};

int main() {
	for(; cin >> X >> Y, X || Y;) {
		int tx, ty;
		int kx, ky;
		cin >> tx >> ty >> kx >> ky;
		tx--, ty--, kx--, ky--;

		memset(visit, 0, sizeof visit);
		memset(field, 0, sizeof field);

		visit[tx][ty][kx][ky] = true;

		for(int y = 0; y < Y; y++) {
			for(int x = 0; x < X; x++) {
				cin >> field[x][y];
			}
		}

		queue<Node> Q;
		Q.push(Node(tx, ty, kx, ky));

		int ans = -1;
		while(!Q.empty()) {
			Node node = Q.front(); Q.pop();
			if(node.turn >= 100) continue;
			if(node.isOk()) {
				ans = node.turn;
				break;
			}
			for(int i = 0; i < 4; i++) {
				Node next = node.move(i);
				if(!visit[next.takx][next.taky][next.kazx][next.kazy]) {
					visit[next.takx][next.taky][next.kazx][next.kazy] = true;
					Q.push(next);
				}
			}
		}

		if(ans == -1) cout << "NA" << endl;
		else cout << ans << endl;
	}
}