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 <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <string>
#include <algorithm>
#include <utility>
#include <vector>
#include <list>
#include <deque>
#include <stack>
#include <queue>
#include <map>
#include <set>
#define INF (2000000000)
#define MOD (1000000007)
using namespace std;

typedef vector<int> VI;
typedef vector<int>::iterator VII;
typedef vector<double> VD;
typedef vector<double>::iterator VDI;
typedef pair<int, int> P;


typedef struct
{
	int tx, ty, kx, ky;
} POS;

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

bool maze[100][100];
int X, Y;
POS f;
int d[52][52][52][52];

int search()
{
	queue<POS> que;
	
	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++){
					d[i][j][k][l] = INF;
				}
			}
		}
	}
	
	que.push(f);
	d[f.tx][f.ty][f.kx][f.ky] = 0;
	
	while (que.size()){
		POS now = que.front();
		que.pop();
		
		//printf("%d %d %d %d\n", now.tx, now.ty, now.kx, now.ky);
		
		if (now.tx == now.kx && now.ty == now.ky){
			return (d[now.tx][now.ty][now.kx][now.ky]);
		}
		
		for (int i = 0; i < 4; i++){
			POS to;
			if (maze[now.tx + dx[i]][now.ty + dy[i]] || maze[now.kx - dx[i]][now.ky - dy[i]]){
				continue;
			}
			else {
				to.tx = now.tx + dx[i];
				to.ty = now.ty + dy[i];
				to.kx = now.kx - dx[i];
				to.ky = now.ky - dy[i];
			}
			
			if (d[to.tx][to.ty][to.kx][to.ky] == INF && d[now.tx][now.ty][now.kx][now.ky] < 100){
				que.push(to);
				d[to.tx][to.ty][to.kx][to.ky] = d[now.tx][now.ty][now.kx][now.ky] + 1;
			}
		}
	}
	
	return (-1);
}

int main()
{
	while (scanf("%d %d", &X, &Y), X + Y){
		scanf("%d %d", &f.tx, &f.ty);
		scanf("%d %d", &f.kx, &f.ky);
		
		for (int i = 0; i < 52; i++){
			for (int j = 0; j < 52; j++){
				maze[i][j] = true;
			}
		}
		
		for (int i = 1; i <= Y; i++){
			for (int j = 1; j <= X; j++){
				scanf("%d", &maze[j][i]);
			}
		}
		
		int r = search();
		if (r != -1) printf("%d\n", r);
		else puts("NA");
	}
	
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()
#define INF 1<<30

using namespace std;

typedef long long ll;
typedef pair<int, int> P;
typedef pair<P,P> PP;
typedef pair<PP,int> PPi;

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

int grid[50][50];
bool vis[50][50][50][50];

/*
struct POS{
	int tx, ty, kx, ky, t;
	POS (int _tx, int _ty, int _kx, int _ky, int _t ) : tx(_tx), ty(_ty), kx(_kx), ky(_ky), t(_t) {}
//	bool operator>(const POS &a ) const{ return t > a.t; }
};
*/
int main()
{
//	cut here before submit 
//	freopen ("testcase.stray_twins", "r", stdin );
	int w, h;
	while (scanf ("%d %d", &w, &h ) && w && h ){
		memset (grid, 0, sizeof (grid ) );
//		memset (vis, false, sizeof (vis ) );

		rep (i, 50 ) rep (j, 50 ) rep (k, 50 ) rep (l, 50 ) vis[i][j][k][l] = false;
			
		int tx, ty, kx, ky;
		scanf ("%d %d %d %d", &tx, &ty, &kx, &ky );
		tx--;ty--;	kx--;ky--;
		rep (i, h ){
			rep (j, w ){
				scanf ("%d", &grid[i][j] );
			} // end rep
		} // end rep

		vis[tx][ty][kx][ky] = true;
//		priority_queue<POS, vector<POS>, greater<POS> > que;
		queue<PPi> que;
		que.push (PPi(PP(P(tx, ty ), P(kx, ky ) ), 0 ) );
		int res = INF;
		while (!que.empty() ){
			PPi curr = que.front(); que.pop();
			int ctx = curr.first.first.first;
			int cty = curr.first.first.second;
			int ckx = curr.first.second.first;
			int cky = curr.first.second.second; 
			int ct  = curr.second;
			rep (k, 4 ){
				int ntx = ctx + dx[k]; int nty = cty + dy[k];
				int nkx = ckx - dx[k]; int nky = cky - dy[k];
				if (ntx < 0 || ntx >= w || nty < 0 || nty >= h || grid[nty][ntx] ){
					ntx = tx; nty = ty;
				} // end if
				if (nkx < 0 || nkx >= w || nky < 0 || nky >= h || grid[nky][nkx] ){
					nkx = kx; nky = ky;
				} // end if
				if (vis[ntx][nty][nkx][nky] || ct + 1 >= 100 ) continue;
				if (ntx == nkx && nty == nky ){
					res = ct+1;
					goto ans;
				} // end if
				vis[ntx][nty][nkx][nky] = true;
				que.push (PPi(PP(P(ntx, nty ), P(nkx, nky ) ), ct+1 ) );
			} // end rep
		} // end while
ans:;
		if (res != INF ){
			printf ("%d\n", res );
		}else{
			printf ("NA\n" );
		} // end if

	} // end loop
		
	return 0;
}