Go: package main

import (
	"container/heap"
	"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)
	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)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		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)
			}
		}
	}
	fmt.Println("NA")
}

func main() {
	var h, w int64
	for {
		fmt.Scan(&h, &w)
		if h == 0 && w == 0 {
			break
		}
		solve(h, w)
	}
}

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;

int board[50][50], Y, X;
int dx[] = {0,1,0,-1}, dy[] = {1,0,-1,0};
bool f[51][51][51][51];

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]);
    memset(f, 0, sizeof(f));

    queue<pii>tq, kq;
    tq.push(make_pair(ty, tx));
    kq.push(make_pair(ky, kx));
    f[ty][tx][ky][kx] = 1;
    int res = 1;
    while(!tq.empty()){
      //      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;

	  if(nt == nk){
	    printf("%d\n", res);
	    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;
	  tq.push(nt); kq.push(nk);
	}
      }
      res++;
      if(res > 100) break;
    }
    //    printf("%d\n", (int)tq.size());
    puts("NA");
  end:;
  }
  return 0;
}

C++: //1.includes
#include<iostream>
#include<queue>
#include<tuple>
#include<algorithm>
using namespace std;
//2.defines
#define MAX_N 60
#define INF 1000000000
//3.variables
int dp[MAX_N][MAX_N][MAX_N][MAX_N];
int H, W, A1, A2, B1, B2;
int x[MAX_N][MAX_N];
queue<tuple<int, int, int, int>>Q;
//4.functions
int solve() {
	dp[A1][A2][B1][B2] = 0;
	Q.push(make_tuple(A1, A2, B1, B2));
	while (!Q.empty()) {
		tuple<int, int, int, int>tup = Q.front();
		Q.pop();
		int a1 = get<0>(tup);
		int a2 = get<1>(tup);
		int a3 = get<2>(tup);
		int a4 = get<3>(tup);
		int dx[4] = { 1,0,-1,0 };
		int dy[4] = { 0,-1,0,1 };
		for (int i = 0; i < 4; i++) {
			int cx = a1 + dx[i], cy = a2 + dy[i];
			int ex = a3 - dx[i], ey = a4 - dy[i];
			if (x[cx][cy] == 1) { cx = a1; cy = a2; }
			if (x[ex][ey] == 1) { ex = a3; ey = a4; }
			if (dp[cx][cy][ex][ey] == INF) {
				dp[cx][cy][ex][ey] = dp[a1][a2][a3][a4] + 1;
				Q.push(make_tuple(cx, cy, ex, ey));
			}
		}
	}
	int minx = INF;
	for (int i = 1; i <= H; i++) {
		for (int j = 1; j <= W; j++) {
			minx = min(minx, dp[i][j][i][j]);
		}
	}
	return minx;
}
void _memset() {
	for (int i = 0; i < MAX_N; i++) {
		for (int j = 0; j < MAX_N; j++) {
			for (int k = 0; k < MAX_N; k++) {
				for (int l = 0; l < MAX_N; l++) {
					dp[i][j][k][l] = INF;
				}
			}
		}
	}
	for (int i = 0; i < MAX_N; i++) {
		for (int j = 0; j < MAX_N; j++) {
			x[i][j] = 1;
		}
	}
}
int main() {
	while (true) {
		_memset();
		cin >> H >> W;
		if (H == 0 && W == 0) { break; }
		cin >> A1 >> A2 >> B1 >> B2;
		for (int i = 1; i <= H; i++) {
			for (int j = 1; j <= W; j++) {
				cin >> x[i][j];
			}
		}
		int v = solve();
		if (v >= 100) { cout << "NA" << endl; }
		else { cout << v << endl; }
	}
	return 0;
}