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 <queue>

typedef std::pair<int, int> P; //(x,y)
typedef std::pair<P, P> PP;
typedef std::pair<PP, int> D;

int x, y;
int map[51][51];
bool visit[51][51][51][51];

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

bool back(P p){
	if(map[p.second][p.first])return true;
	else if(p.second < 0 || p.second >= y || p.first < 0 || p.first >= x)return true;
	else return false;
}

int main(){
	while(true){
		for(int i = 0; i < 51; ++i)for(int j = 0; j < 51; ++j)for(int k = 0; k < 51; ++k)for(int l = 0; l < 51; ++l)visit[i][j][k][l] = false;
		
		std::cin >> x >> y;
		if(x == 0 && y == 0)break;
		
		P t, k;
		std::cin >> t.first >> t.second;
		std::cin >> k.first >> k.second;
		--t.first, --t.second;
		--k.first, --k.second;

		for(int i = 0; i < y; ++i){
			for(int j = 0; j < x; ++j){
				std::cin >> map[i][j];
			}
		}

		bool f = false;

		std::queue<D> que;
		que.push(D(PP(t, k), 0));

		while(!que.empty()){
			D d = que.front();
			que.pop();
			
			P ct = d.first.first, ck = d.first.second;
			visit[ct.first][ct.second][ck.first][ck.second] = true;
			
			if(d.second >= 100){
				break;
			}
			if(ct == ck){
				f = true;
				std::cout << d.second << std::endl;
				break;
			}
			
			for(int i = 0; i < 4; ++i){
				P nt = ct, nk = ck;
				nt.first += dx[i]; nt.second += dy[i];
				nk.first -= dx[i]; nk.second -= dy[i];
				
				if(back(nt))nt = ct;
				if(back(nk))nk = ck;
				
				if(visit[nt.first][nt.second][nk.first][nk.second])continue;
				que.push(D(PP(nt, nk), d.second + 1));
			}
		}
		
		if(!f)std::cout << "NA" << std::endl;
	}
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <queue>
#include <complex>

using namespace std;

#define INF 1 << 20

typedef complex<int> P;

struct point {
	P p1, p2;
	int step;

	point(P p1, P p2, int step) : p1(p1), p2(p2), step(step) { }
	point() { this -> p1 = this -> p2 = P(0, 0); this -> step = 0; }
};

bool step[50][50][50][50] = {0};

int main() {
	int W, H;
	while (cin >> W >> H, W || H) {
		int s1x, s1y; cin >> s1x >> s1y;
		int s2x, s2y; cin >> s2x >> s2y;

		int wall[50][50];
		for (int y = 0; y < H; ++y)
			for (int x = 0; x < W; ++x)
				cin >> wall[y][x];

		bool f = false; fill(&step[0][0][0][0], &step[0][0][0][0]+50*50*50*50, false);
		queue<point> que; que.push( point( P(s1x-1, s1y-1), P(s2x-1, s2y-1), 0 ) );
		queue<P> dirs; dirs.push( P(0, 0) );
		while ( !que.empty() ) {
			point p = que.front(); que.pop();
			P dir = dirs.front(); dirs.pop();

			p.p1 += dir, p.p2 -= dir;

			if (p.step >= 100) continue;
			if (p.p1.real() < 0 || p.p1.real() >= W || p.p1.imag() < 0 || p.p1.imag() >= H) p.p1 -= dir;
			if (p.p2.real() < 0 || p.p2.real() >= W || p.p2.imag() < 0 || p.p2.imag() >= H) p.p2 += dir;
			if (wall[p.p1.imag()][p.p1.real()]) p.p1 -= dir;
			if (wall[p.p2.imag()][p.p2.real()]) p.p2 += dir;
			if (step[p.p1.real()][p.p1.imag()][p.p2.real()][p.p2.imag()]) continue;
			step[p.p1.real()][p.p1.imag()][p.p2.real()][p.p2.imag()] = true;

			if (wall[p.p1.imag()][p.p1.real()]) continue;
			if (wall[p.p2.imag()][p.p2.real()]) continue;

// cout << p.p1.real() << " " << p.p1.imag() << " " << p.p2.real() << " " << p.p2.imag() << endl;

			if (p.p1 == p.p2) {
				cout << p.step << endl;
				f = true;
				break;
			}

			++p.step;
			que.push(p); dirs.push( P(1, 0) );
			que.push(p); dirs.push( P(-1, 0) );
			que.push(p); dirs.push( P(0, 1) );
			que.push(p); dirs.push( P(0, -1) );
		}
		if (f) continue;
		cout << "NA" << endl;

	}
}