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 ans <= now.Turn {
			continue
		}
		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 <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <numeric>

using namespace std;

#ifdef _MSC_VER
#define __typeof__ decltype

template <class T>
int __builtin_popcount(T n) { return n ? 1 + __builtin_popcount(n & (n - 1)) : 0; }
#endif

#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define popcount __builtin_popcount

const double EPS = 1e-8;
typedef long long ll;
typedef pair<int, int> pint;


int X, Y, depa[50][50];
int dx[] = { 0, 1, 0, -1 };
int dy[] = { 1, 0, -1, 0 };
void move(int x, int y, int dir, int* nx, int* ny)
{
	int tx = x + dx[dir];
	int ty = y + dy[dir];
	if (tx >= 0 && ty >= 0 && tx < X && ty < Y
		&& depa[ty][tx] == 0
		)
	{
		*nx = tx;
		*ny = ty;
	}
	else
	{
		*nx = x;
		*ny = y;
	}
}
int enc(int tx, int ty, int kx, int ky)
{
	return tx | ty << 6 | kx << 6*2 | ky << 6*3;
}
void dec(int e, int& tx, int& ty, int& kx, int &ky)
{
	const int mask = (1 << 6) - 1;
	tx = e & mask;
	ty = e >> 6 & mask;
	kx = e >> 6*2 & mask;
	ky = e >> 6*3 & mask;
}
map<int, int> memo;
int main()
{
	while (scanf("%d%d", &X, &Y), X|Y)
	{
		int tx, ty, kx, ky;
		scanf("%d%d%d%d", &tx, &ty, &kx, &ky);
		for (int i = 0; i < Y; ++i)
			for (int j = 0; j < X; ++j)
				scanf("%d", &depa[i][j]);
		memo.clear();

		queue<int> q;
		q.push(enc(tx, ty, kx, ky));
		memo[enc(tx, ty, kx, ky)] = 0;
		int res = -1;
		while (!q.empty())
		{
			int e = q.front(); q.pop();
			int time = memo[e];

			dec(e, tx, ty, kx, ky);
			if (tx == kx && ty == ky)
			{
				res = time;
				break;
			}

			if (time >= 99)
				continue;

			for (int i = 0; i < 4; ++i)
			{
				int ttx, tty, kkx, kky;
				move(tx, ty, i, &ttx, &tty);
				move(kx, ky, (i+2)%4, &kkx, &kky);

				int en = enc(ttx, tty, kkx, kky);
				if (!memo.count(en))
				{
					memo[en] = time + 1;
					q.push(en);
				}
			}
		}
		if (res != -1)
			printf("%d\n", res);
		else
			puts("NA");
	}

	return 0;
}

C++: #include <iostream>
#include <queue>
#include <cstring>

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[52][52];
bool memo[52][52][52][52];
int tx, ty, kx, ky;

void solve()
{
    int ans = -1;
    state s(tx, ty, kx, ky, 0);
    queue<state> q;
    
    memset(memo, 0, sizeof(memo));

    q.push(s);
    memo[ty][tx][ky][kx] = 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;
            }
                
            if (memo[nty][ntx][nky][nkx] == true)
                continue;
            state next(ntx, nty, nkx, nky, now.time + 1);
            q.push(next);
            memo[nty][ntx][nky][nkx] = 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;
}