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)
	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)
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		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)
			}
		}
	}
	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 <algorithm>
#include <queue>
#include <cstring>

using namespace std;

typedef pair<int, int> Pii;
typedef pair<int, pair<Pii, Pii> > Tpl;
#define fi first
#define se second
int W, H;
int const INF = 1<<29;
inline bool inF(int x, int y) {
  return 0<=x&&x<W&&0<=y&&y<H;
}

int main() {

  int const dx[] = {-1,0,1,0};
  int const dy[] = {0,-1,0,1};
  while(cin >> W >> H && (W|H)) {
    int tx, ty, kx, ky; cin >> tx >> ty >> kx >> ky; tx--; ty--; kx--; ky--;
    int grid[51][51];
    for(int i=0; i<H; i++)
      for(int j=0; j<W; j++)
	cin >> grid[i][j];
    
    static int vis[51][51][51][51];
    fill(vis[0][0][0], vis[51][0][0], INF);
    
    queue<Tpl> Q;
    Q.push(Tpl(make_pair(0, make_pair(Pii(tx, ty), Pii(kx, ky)))));
    vis[ty][tx][ky][kx] = 0;
    int ans = -1;
    while(!Q.empty()) {
      Tpl t = Q.front(); Q.pop();
      const int tx = t.se.fi.fi, ty = t.se.fi.se, kx = t.se.se.fi, ky = t.se.se.se;
      const int cost = t.fi;
      for(int i=0; i<4; i++) {
	int ntx = tx+dx[i], nty = ty+dy[i];
	int nkx = kx-dx[i], nky = ky-dy[i];
	if(tx == kx && ty == ky) { ans = cost; goto EXIT; }
	if(!inF(ntx, nty) && !inF(nkx, nky)) continue;
	if(!inF(ntx, nty)) ntx = tx, nty = ty;
	if(!inF(nkx, nky)) nkx = kx, nky = ky;
	if(grid[nty][ntx] && grid[nky][nkx]) continue;
	if(grid[nty][ntx]) ntx = tx, nty = ty;
	if(grid[nky][nkx]) nkx = kx, nky = ky;
	if(vis[nty][ntx][nky][nkx] > cost+1) {
	  vis[nty][ntx][nky][nkx] = cost+1;
	  Q.push(Tpl(cost+1, make_pair(Pii(ntx, nty), Pii(nkx, nky))));
	}
      }
    }
    
  EXIT:;
    if(ans == -1) cout << "NA" << endl;
    else cout << ans << endl;
  }
  
  return 0;
}