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(101)
	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 v, ok := memo[now.Person]; ok && v <= now.Turn {
			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 += 1
			if next.Turn < 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				pq = append(pq, next)
			}
		}
	}
	if ans == 101 {
		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 <string>
#include <vector>
#include <cstring>
#include <climits>
#include <algorithm>
#include <map>
using namespace std;

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

int X, Y;
int d[52][52];
int mintime[52][52][52][52];

void dfs(int tx, int ty, int kx, int ky, int t, int &mint) {
    if (tx == kx && ty == ky) {
        mint = min(t, mint);
        return ;
    }
    if (mint <= t) {
        return ;
    }
    mintime[tx][ty][kx][ky] = min(mintime[tx][ty][kx][ky], t);
    for (int i=0; i<4; ++i) {
        if (d[ty+dy[i]][tx+dx[i]] && d[ky-dy[i]][kx-dx[i]]) continue;
        int tx2 = tx, ty2 = ty;
        if ( ! d[ty+dy[i]][tx+dx[i]]) {
            tx2 += dx[i];
            ty2 += dy[i];
        }
        int kx2 = kx, ky2 = ky;
        if ( ! d[ky-dy[i]][kx-dx[i]]) {
            kx2 -= dx[i];
            ky2 -= dy[i];
        }
        if (t+1 < mintime[tx2][ty2][kx2][ky2]) {
            dfs(tx2, ty2, kx2, ky2, t+1, mint);
        }
    }
}

int main() {
    while (cin >> X >> Y, X) {
        int tx, ty, kx, ky;
        cin >> tx >> ty >> kx >> ky;
        for (int i=0; i<=Y+1; ++i) {
            for (int j=0; j<=X+1; ++j) {
                if (i==0 || i==Y+1 || j==0 || j==X+1) d[i][j] = 1;
                else cin >> d[i][j];
            }
        }
        for (int i=0; i<52; ++i) for (int j=0; j<52; ++j) {
            for (int k=0; k<52; ++k) for (int l=0; l<52; ++l) {
                mintime[i][j][k][l] = 101;
            }
        }
        int mint = 101;
        dfs(tx, ty, kx, ky, 0, mint);
        if (mint == 101) {
            cout << "NA" << endl;
        } else {
            cout << mint << endl;
        }
    }
    return 0;
}

C++: #include<cstdio>
#include<iostream>
#include<string>
#include<map>
#include<queue>
#include<set>

using namespace std;

#define rep(i,n) for(int i=0;i<n;i++)
#define reps(i,n) for(int i=1;i<=n;i++)

class S{
	public:
	char a,b,c,d;
	int val;
	S(int a,int b,int c,int d,int val):
	a(a),b(b),c(c),d(d),val(val){}
};

char ch[55][55][55][55];

int main(){
	while(1){
		int n,m;
		cin>>n>>m;
		if(n==0)break;
		
		int sa,sb,sc,sd;
		cin>>sa>>sb>>sc>>sd;
		
		int masu[55][55]={0};
		reps(i,n){
			reps(j,m){
				cin>>masu[i][j];
			}
		}
		
		rep(i,55)rep(j,55)rep(k,55)rep(p,55)ch[i][j][k][p]=0;
		
		queue<S> que;
		que.push(S(sb,sa,sd,sc,0));
		
		int dx[4]={-1,0,1,0};
		int dy[4]={0,1,0,-1};
		
		int ans=-1;
		while(1){
			if(que.empty())break;
			
			S u = que.front();
			que.pop();
			
			
			if(u.a<=0 || u.b<=0 || u.c<=0 || u.d<=0)continue;
			if(u.a>m || u.c>m || u.b>n || u.d>n)continue;
			
			if(ch[u.a][u.b][u.c][u.d]==1)continue;
			ch[u.a][u.b][u.c][u.d]=1;
			
			printf("%d %d  %d %d  %d\n",u.a,u.b,u.c,u.d,u.val);
			
			if(masu[u.a][u.b]==1 || masu[u.c][u.d]==1)continue;
			
			if(u.a == u.c && u.b==u.d){
				ans = u.val;
				break;
			}
			
			S e = u;
			e.val++;
			rep(i,4){
				e.a += dx[i];
				e.b += dy[i];
				e.c -= dx[i];
				e.d -= dy[i];
					
				if(masu[e.a][e.b]==1 || masu[e.c][e.d]==1){
				}else if(ch[e.a][e.b][e.c][e.d]==1){
				}else{
					que.push(e);
				}
				
				e.c += dx[i];
				e.d += dy[i];
				e.a -= dx[i];
				e.b -= dy[i];
			}
		}
		if(ans==-1){
			puts("NA");
		}else
		printf("%d\n",ans);
	}
}

C++: #include <iostream>
#include <queue>
#include <algorithm>

using namespace std;

struct State{
  int tx, ty, kx, ky;
  State(int tx, int ty, int kx, int ky) : tx(tx), ty(ty), kx(kx), ky(ky) {} 
};

#define MAX 51
#define INF 1e9

int H, W, tx, ty, kx, ky;
int field[MAX][MAX];
const int ttx[] = {-1,0,0,1};
const int tty[] = {0,-1,1,0};
const int kkx[] = {1,0,0,-1};
const int kky[] = {0,1,-1,0};

bool inField(int y, int x){
  return 0 <= y && y < H && 0 <= x && x < W;
}

int bfs(){
  bool vis[MAX][MAX][MAX][MAX];
  memset(vis, false, sizeof(vis));
  vis[ty][tx][ky][kx] = true;
  queue<State> Q;
  Q.push(State(tx,ty,kx,ky));
  queue<int> cnt;
  cnt.push(0);

  int res = INF;
  while(!Q.empty()){
    State s = Q.front(); Q.pop();
    int _cnt = cnt.front(); cnt.pop();

    if(_cnt == 100) break;
    if(s.tx == s.kx && s.ty == s.ky){
      res = min(res, _cnt);
      break;
    }

    for(int i = 0 ; i < 4 ; i++){
      int ntx = s.tx + ttx[i], nty = s.ty + tty[i];
      int nkx = s.kx + kkx[i], nky = s.ky + kky[i];

      if(!inField(nty, ntx) || field[nty][ntx] == 1){
        ntx = s.tx, nty = s.ty;
      }
      if(!inField(nky, nkx) || field[nky][nkx] == 1){
        nkx = s.kx, nky = s.ky;
      }

      if(vis[nty][ntx][nky][nkx]) continue;
      vis[nty][ntx][nky][nkx] = true;
      Q.push(State(ntx, nty, nkx, nky));
      cnt.push(_cnt+1);
    }
  }
  return res;
}

int main(){
  while(cin >> W >> H, (W | H)){
    cin >> tx >> ty >> kx >> ky;
    tx--, ty--, kx--, ky--;
    for(int i = 0 ; i < H ; i++){
      for(int j = 0 ; j < W ; j++){
        cin >> field[i][j];
      }
    }
    int res = bfs();
    if(res == INF){
      cout << "NA" << endl;
    }else{
      cout << res << endl;
    }
  }

  return 0;
}