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 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 <iostream>
#include <queue>
#include <cstring>

constexpr int MAX = 50;
using P = std::pair<int, int>;
using MyP = std::pair<P, P>;

int w, h;

bool board[MAX][MAX];
int d[MAX][MAX][MAX][MAX];//tx,ty,kx,ky
constexpr int dx[] = { -1,0,1,0 }, dy[] = { 0,-1,0,1 };

int bfs(P ts, P ks) {
	std::memset(d, -1, sizeof(d));
	std::queue<MyP> que;
	d[ts.first][ts.second][ks.first][ks.second] = 0;
	que.emplace(ts, ks);

	while (!que.empty()) {
		MyP p = que.front(); que.pop();
		P t = p.first, k = p.second;
		if (d[t.first][t.second][k.first][k.second] >= 100)
			break;
		std::cout << t.first << ' ' << t.second << std::endl;
		if (t == k)
			return d[t.first][t.second][k.first][k.second];
		int nx[2], ny[2];
		for (int i = 0; i < 4; ++i) {

			nx[0] = t.first + dx[i];
			ny[0] = t.second + dy[i];
			nx[1] = k.first - dx[i];
			ny[1] = k.second - dy[i];

			if (0 <= nx[0] && nx[0] < w &&
				0 <= ny[0] && ny[0] < h&&!board[ny[0]][nx[0]]) {
				if (0 <= nx[1] && nx[1] < w &&
					0 <= ny[1] && ny[1] < h && !board[ny[1]][nx[1]] && d[nx[0]][ny[0]][nx[1]][ny[1]] == -1) {
					d[nx[0]][ny[0]][nx[1]][ny[1]] =
						d[t.first][t.second][k.first][k.second] + 1;
					que.emplace(P(nx[0], ny[0]), P(nx[1], ny[1]));
				}
				else if (d[nx[0]][ny[0]][k.first][k.second] == -1) {
					d[nx[0]][ny[0]][k.first][k.second] =
						d[t.first][t.second][k.first][k.second] + 1;
					que.emplace(P(nx[0], ny[0]), k);
				}
			}
			else if (0 <= nx[1] && nx[1] < w &&
				0 <= ny[1] && ny[1] < h && !board[ny[1]][nx[1]] && d[t.first][t.second][nx[1]][ny[1]] == -1) {
				d[t.first][t.second][nx[1]][ny[1]] =
					d[t.first][t.second][k.first][k.second] + 1;
				que.emplace(t, P(nx[1], ny[1]));
			}
		}
	}
	return -1;
}

int main() {
	while (1) {
		std::cin >> w >> h;
		if (w + h == 0)
			break;
		P ts, ks;
		std::cin >> ts.first >> ts.second
			>> ks.first >> ks.second;
		--ts.first;
		--ts.second;
		--ks.first;
		--ks.second;
		for (int i = 0; i < h; ++i) {
			for (int j = 0; j < w; ++j)
				std::cin >> board[i][j];
		}
		int ans = bfs(ts, ks);
		if (ans == -1)
			std::cout << "NA" << std::endl;
		else
			std::cout << ans << std::endl;
	}
	return 0;
}