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>
#include<cstring>
using namespace std;

int x,y,tx,ty,kx,ky,cou;
int mas[51][51];
int ans=0;
bool used[51][51][51][51];
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<bits/stdc++.h>
using namespace std;

struct coor {
    int x, y;
    coor(const int& y_ = 0, const int& x_ = 0) : y(y_), x(x_) {}
    bool operator==(coor& a) { return x == a.x && y == a.y;}
    bool in(int& H, int&W){
        return 0 <= y && y < H && 0 <= x && x < W; 
    }
};

const int dy[4] = {1,-1, 0, 0};
const int dx[4] = {0, 0, 1, -1};
int dist[51][51][51][51];

void ClearDist(){
    #define rep(i, N) for(int i = 0; i < N; i++)
    
    const int N = 51;
    rep(a,N)rep(b,N)rep(c,N)rep(d,N) dist[a][b][c][d] = -1;
}

int solve(int W, int H){
    int tx, ty;
    int kx, ky;
    cin >> tx >> ty; tx--, ty--;
    cin >> kx >> ky; kx--, ky--;
    vector<vector<int>> grid(H, vector<int>(W));
    for(int h = 0; h < H; h++){
        for(int w = 0; w < W; w++){
            cin >> grid[h][w];
        }
    }
    
    ClearDist();
    dist[ty][tx][ky][kx] = 0;
    coor taka = coor(ty, tx);
    coor kazu = coor(ky, kx);
    int ans = (taka == kazu ? 0 : 100);
    queue<pair<coor, coor>> que;
    que.push({taka, kazu});
    
    while(!que.empty()){
        tie(taka, kazu) = que.front();
        que.pop();

        for(int i = 0; i < 4; i++){
            coor n_taka = coor(taka.y + dy[i], taka.x + dx[i]);
            coor n_kazu = coor(kazu.y - dy[i], kazu.x - dx[i]);
            
            if(!n_taka.in(H, W) && !n_kazu.in(H, W)) continue;

            if(!n_taka.in(H, W) || grid[n_taka.y][n_taka.x] == 1) n_taka = taka;
            if(!n_kazu.in(H, W) || grid[n_kazu.y][n_kazu.x] == 1) n_kazu = kazu;
            if(n_taka == taka && n_kazu == kazu) continue;

            int& nxt = dist[n_taka.y][n_taka.x][n_kazu.y][n_kazu.x];
            if(nxt != -1) continue;

            nxt = dist[taka.y][taka.x][kazu.y][kazu.x] + 1;
            if(n_taka == n_kazu) ans = min(ans, nxt);
            if(nxt < 100) que.push({n_taka, n_kazu});
        }
        
    }
    
    return ans;
}

int main(){
    int W, H;
    while(cin >> W >> H, W != 0){
        int ans = solve(W, H);
        if(ans >= 100) cout << "NA" << endl;
        else cout << ans << endl;
    }
}