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 <map>
#include <queue>
#include <sstream>
#include <cmath>

using namespace std;

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

class state {
public:
    int tx, ty;
    int kx, ky;
    int time;
    state(int a, int b, int c, int d, int e) {
        tx = a;
        ty = b;
        kx = c;
        ky = d;
        time = e;
    }
};

int h, w;
int grid[55][55];
int tx, ty, kx, ky;

int dis(int x1, int y1, int x2, int y2)
{
    return abs(y2 - y1) + abs(x2 - x1);
}

void solve()
{
    int ans = -1;
    state s(tx, ty, kx, ky, 0);
    map<string, bool> m;
    queue<state> q;
    ostringstream oss;

    oss << tx << "," << ty << "," << kx << "," << ky;
    q.push(s);
    m[oss.str()] = true;

    while (!q.empty()) {
        state now = q.front();
        q.pop();

        if (now.time >= 100)
            break;
        if (now.tx == now.kx && now.ty == now.ky) {
            ans = now.time;
            break;
        }

        for (int i = 0; i < 4; i++) {
            int ntx = now.tx + dx[i];
            int nty = now.ty + dy[i];
            int nkx = now.kx + dx[(i + 2) % 4];
            int nky = now.ky + dy[(i + 2) % 4];

            if (ntx < 1 || ntx > w)
                ntx = now.tx;
            if (nty < 1 || nty > h)
                nty = now.ty;
            if (nkx < 1 || nkx > w)
                nkx = now.kx;
            if (nky < 1 || nky > h)
                nky = now.ky;
            if (grid[nty][ntx] != 0) {
                ntx = now.tx;
                nty = now.ty;
            }
            if (grid[nky][nkx] != 0) {
                nkx = now.kx;
                nky = now.ky;
            }
                
            oss.str("");
            oss << ntx << "," << nty << "," << nkx << "," << nky;

            if (m.count(oss.str()) != 0)
                continue;
            if (dis(ntx, nty, nkx, nky) > dis(now.tx, now.ty, now.kx, now.ky))
                continue;
            state next(ntx, nty, nkx, nky, now.time + 1);
            q.push(next);
            m[oss.str()] = true;
        }
    }
    if (ans == -1 || ans >= 100)
        cout << "NA" << endl;
    else
        cout << ans << endl;
}

int main()
{
    while (cin >> w >> h, w || h) {
        cin >> tx >> ty >> kx >> ky;
        for (int y = 1; y <= h; y++)
            for (int x = 1; x <= w; x++) 
                cin >> grid[y][x];
        solve();
    }

    return 0;
}

C++: #include <iostream>
#include <queue>
#include <cstring>
using namespace std;

int field[50][50];
bool visit[50][50][50][50];

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

int main()
{
	int w,h,ax,ay,bx,by;

	while(cin >> w >> h, w||h)
	{
		cin >> ax >> ay;
		cin >> bx >> by;

		for(int y=0; y<h; y++)
		for(int x=0; x<w; x++)
		{
			cin >> field[y][x];
		}
		memset(visit,0,sizeof(visit));

		int cnt=0;
		bool flag=false;
		queue<int> q;
		q.push(ax-1);
		q.push(ay-1);
		q.push(bx-1);
		q.push(by-1);
		while(!q.empty())
		{
			int len=q.size()/4;
			for(int l=0; l<len; l++)
			{
				ax=q.front(); q.pop();
				ay=q.front(); q.pop();
				bx=q.front(); q.pop();
				by=q.front(); q.pop();

				if(ax==bx && ay==by)
				{
					flag=true;
					break;
				}
				visit[ax][ay][bx][by] = 1;

				for(int d=0; d<4; d++)
				{
					int px = ax+dx[d];
					int py = ay+dy[d];
					int qx = bx-dx[d];
					int qy = by-dy[d];

					if(px<0 || w<=px || py<0 || h<=py) { px=ax; py=ay; }
					if(qx<0 || w<=qx || qy<0 || h<=qy) { qx=bx; qy=by; }
					if(field[py][px]) { px=ax; py=ay; }
					if(field[qy][qx]) { qx=bx; qy=by; }

					if(!visit[px][py][qx][qy])
					{
						q.push(px);
						q.push(py);
						q.push(qx);
						q.push(qy);
					}
				}
			}

			if(flag) break;

			cnt++;
		}

		if(flag)
		{
			cout << cnt << endl;
		}
		else
		{
			cout << "NA" << endl;
		}
	}

}