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 (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.Init(&pq)
	//heap.Push(&pq, start)
	//pq.Push(start)
	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 pq.Len() > 0 {
		//now := heap.Pop(&pq).(*Status)
		//now := pq.Pop().(*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]
			}
			if now==next {
				continue
			}
			next.Turn += 1
			if next.Turn <= 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				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<stdio.h>
#include<string.h>
#include<queue>
using namespace std;

struct AO
{
	int tx;
	int ty;
	int kx;
	int ky;
	int cnt;
};

queue<AO> Q;
AO TK,f;
int d[51][51];
int sa[51][51][51][51];

int main()
{
	int X,Y,F; //     tx ty kx ky
	int mv[4][4] ={{ 0,-1, 0, 1}, //???
				   { 0, 1, 0,-1}, //???
				   {-1, 0, 1, 0}, //???
				   { 1, 0,-1, 0}};//???
	while(1){
		F = 1;
		for(int i=0;i<52;i++){
			for(int j=0;j<52;j++){
				d[i][j] = 1;
			}
		}
		memset(sa,0,sizeof(sa));
		//printf("%d\n",d[0][0]);
		scanf("%d %d",&X,&Y);
		if(X == 0 && Y == 0) break;
		scanf("%d %d %d %d",&TK.tx,&TK.ty,&TK.kx,&TK.ky);
		sa[TK.ty][TK.tx][TK.ky][TK.kx] = 1;
		TK.cnt = 0;
		Q.push(TK);
		for(int i=1;i<=Y;i++){
			for(int j=1;j<=X;j++){
				scanf("%d",&d[i][j]);
			}
		}

		while(!Q.empty()){    //!Q.empty()
			TK = Q.front();
			Q.pop();
			//printf("?????? ??????:%d %d  ??????:%d %d\n",TK.tx,TK.ty,TK.kx,TK.ky);
			if(TK.cnt >= 100){
				break;
			}
			if(TK.tx == TK.kx && TK.ty == TK.ky){
				F = 0;
				break;
			}
			if(TK.cnt >= 100){
				break;
			}
			for(int i=0;i<4;i++){
				f.tx = TK.tx + mv[i][0];
				f.ty = TK.ty + mv[i][1];
				f.kx = TK.kx + mv[i][2];
				f.ky = TK.ky + mv[i][3];
				f.cnt = TK.cnt + 1;
				//printf("A");
				if(d[f.ty][f.tx] == 0 || d[f.ky][f.kx] == 0){
					if(d[f.ty][f.tx] == 1){
						f.tx = TK.tx;
						f.ty = TK.ty;
					}
					if(d[f.ky][f.kx] == 1){
						f.kx = TK.kx;
						f.ky = TK.ky;
					}
				}
				else if(d[f.ty][f.tx] == 1 && d[f.ky][f.kx] == 1){
					continue;
				}
				if(  sa[f.ty][f.tx][f.ky][f.kx] == 1 || f.tx < 0 || f.kx < 0 || f.ty < 0 || f.ky < 0 || f.tx > X || f.kx > X || f.ty > Y || f.ky > Y){
					continue;
				}
				sa[f.ty][f.tx][f.ky][f.kx] = 1;
				Q.push(f);
				//printf("??????%d %d\n?????? %d %d\n",f.tx,f.ty,f.kx,f.ky);
			}
			//printf("------------\n");
		}
		if(F==0)
			printf("%d\n",TK.cnt);
			//printf("%d %d %d %d\n",TK.tx,TK.ty,TK.kx,TK.ky);
		else
			printf("NA\n");
		while(!Q.empty())
			Q.pop();
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>

using namespace std;

#define rep(i,j) REP((i), 0, (j))
#define REP(i,j,k) for(int i=(j);(i)<(k);++i)
#define BW(x,b) ((x)>=0&&(x)<(b))
#define Y first
#define X second
#define INF 1 << 30

typedef pair<int, int> pii;
typedef queue<int> qi;
typedef pair<int, int> pi;

int board[51][51], Y, X;
int dx[] = {0,1,0,-1}, dy[] = {1,0,-1,0};

pii nextp1(pii now, int i){
  pii next = now;
  next.Y += dy[i];
  next.X += dx[i];
  //  printf("%d %d\n", next.Y, next.X);
  //  if(BW(next.Y, Y)) puts("YES");
  //  if(BW(next.X, X)) puts("YES");
  //  printf("%d\n", board[next.Y][next.X]);
  if(BW((next.Y), Y) && BW((next.X), X) && board[next.Y][next.X] == 0) return next;
  return now;
}

pii nextp2(pii now, int i){
  pii next = now;
  next.Y += -1 * dy[i];
  next.X += -1 * dx[i];
  if(BW(next.Y, Y) && BW(next.X, X) && board[next.Y][next.X] == 0) return next;
  return now;
}
     
int main(){
  while(scanf("%d%d", &X,  &Y) && X+Y){
    int tx, ty, kx, ky;
    scanf("%d%d%d%d", &tx, &ty, &kx, &ky); tx--; ty--; kx--; ky--;
    rep(i, X) rep(j, Y) scanf("%d", &board[i][j]);

    map<pair<pi,pi>, bool>m; // t k
    queue<pii>tq, kq;
    tq.push(make_pair(ty, tx));
    kq.push(make_pair(ky, kx));
    m[make_pair(make_pair(ty, tx), make_pair(ky, kx))] = 1;
    int res = 1;
    while(!tq.empty()){
      //      if(res > 100) break;
      //      printf("%d", res);
      int qsize = (int)tq.size();
      //      printf(" %d\n", qsize);
      rep(i, qsize){
	pii t = tq.front(); tq.pop();
	pii k = kq.front(); kq.pop();
	//	printf("%d %d %d %d\n", t.Y, t.X, k.Y, k.X);
	rep(j, 4){
	  pii nt = nextp1(t, j), nk = nextp2(k, j);
	  //	  printf("%d %d %d %d\n", nt.Y, nt.X, nk.Y, nk.X);

	  //	  if(f[nt.Y][nt.X][nk.Y][nk.X]) continue;
	  pair<pi, pi> next = make_pair(make_pair(nt.Y, nt.X), make_pair(nk.Y, nk.X));
	  if(m.count(next) == 1) continue;
	  if(nt == nk){
	    printf("%d\n", res);
	    //	    printf("%d %d %d %d\n", nt.Y, nt.X, nk.Y, nk.X);
	    goto end;
	  }
	  //	  fprintf(stderr, "%d %d %d %d\n", nt.Y, nt.X, nk.Y, nk.X);
	  //	  f[nt.Y][nt.X][nk.Y][nk.X] = 1;
	  m[next] = 1;
	  tq.push(nt); kq.push(nk);
	}
      }
      if(res > 100) break;
      res++;

    }
    //    printf("%d\n", (int)tq.size());
    puts("NA");
  end:;
  }
  return 0;
}