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(102)
	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 _, ok := memo[now.Person]; ok {
			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++
			if next.Turn <= 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				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 <algorithm>
#include <queue>

using namespace std;

const int inf = 999999;

struct P{
	int x;
	int y;
};

struct St{
	P tk;
	P kz;
	int cost;
};

int xdir[4] = {0, 1, 0, -1}, ydir[4] = {1, 0, -1, 0};

int bfs(char a[51][51], int w, int h, P p, P q)
{
	int r = inf;
	bool vis[51][51][51][51];
	fill(&vis[0][0][0][0], &vis[50][50][50][50], true);
	St s, t;
	queue<St> que;
	s.tk = p;
	s.kz = q;
	s.cost = 0;
	que.push(s);
	
	while(!que.empty()){
		s = que.front();
		que.pop();
		if(s.tk.x == s.kz.x && s.tk.y == s.kz.y){
			r = s.cost;
			break;
		}
		if(s.cost > 100){
			break;
		}
		
		for(int i = 0; i < 4; i++){
			int tx = s.tk.x+xdir[i], ty = s.tk.y+ydir[i];
			int kx = s.kz.x-xdir[i], ky = s.kz.y-ydir[i];
			if(0 <= tx && tx < w && 0 <= ty && ty < h && 0 <= kx && kx < w && 0 <= ky && ky < h){
				if(a[ty][tx] == '0' && a[ky][kx] == '0' && vis[ty][tx][ky][kx]){
					vis[ty][tx][ky][kx] = false;
					t.tk.x = tx;
					t.tk.y = ty;
					t.kz.x = kx;
					t.kz.y = ky;
					t.cost = s.cost+1;
					que.push(t);
				}
			}
		}
	}
	
	return r;
}

int main()
{
	int w, h, r;
	char a[51][51];
	P p, q;
	
	while(cin>>w>>h && (w+h)){
		cin >> p.x >> p.y;
		cin >> q.x >> q.y;
		for(int i = 0; i < h; i++){
			for(int j = 0; j < w; j++){
				cin >> a[i][j];
			}
		}
		
		r = bfs(a, w, h, p, q);
		if(r == inf){
			cout << "NA" << endl;
		} else {
			cout << r << endl;
		}
	}
	
	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;

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

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

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;
		scanf ("%d %d", &tx, &ty );
		tx--;ty--;
		int kx, ky;
		scanf ("%d %d", &kx, &ky );
		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<POS> que;
		que.push (POS (tx, ty, kx, ky, 0 ) );
		int res = INF;
		while (!que.empty() ){
			POS curr = que.front(); que.pop();
			int ctx = curr.tx;
			int cty = curr.ty;
			int ckx = curr.kx;
			int cky = curr.ky; 
			int ct  = curr.t;
			rep (k, 4 ){
				int ntx = ctx + dx[k], nty = cty + dy[k];
				int nkx = ckx - dx[k], 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 (POS (ntx, nty, 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;
}