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 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)
	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 len(pq) > 0 {
		now := &Status{}
		now = pq[0]
		pq = pq[1:]
		if ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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 {
				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<cstdio>
#include<queue>
#include<map>
#include<algorithm>
#include<cstring>
#include<string.h>
using namespace std;
struct P{
  int tx,ty;
  int kx,ky;
  int cost;
  P(int _tx, int _ty, int _kx, int _ky, int _cost) : tx(_tx), ty(_ty), kx(_kx), ky(_ky), cost(_cost) {};
};
int hx,hy,rx,ry;
int X,Y;
int mas[110][110];
bool d[51][51][51][51];
int dx[4] = {0,1,0,-1},dy[4] = {1,0,-1,0};
int bfs();
int main(){
  while(1){
    scanf("%d %d",&X,&Y);
    if(X == 0 && Y == 0)break;
    scanf("%d %d",&hx,&hy);
    scanf("%d %d",&rx,&ry);
    for(int i = 1; i <= Y; i++){
      for(int j = 1; j <= X; j++){
	scanf("%d",&mas[i][j]);
      }
    }
    int ans = bfs();
    if(ans == -1)cout << "NA" << endl;
    else cout << ans << endl;
  }
}
int bfs(){
  queue<P> que;
  memset(d,0,sizeof(d));
  que.push(P(hx,hy,rx,ry,0));
  d[hx][hy][rx][ry] = 0;
  while(!que.empty()){
    P p = que.front();
    que.pop();
    if(p.cost >= 100)return -1;
    if(p.tx == p.kx && p.ty == p.ky){
      return p.cost;
    }
    for(int i = 0; i < 4; i++){
      int nx = p.tx + dx[i], ny = p.ty + dy[i];
      int ux = p.kx - dx[i], uy = p.ky - dy[i];
      if(nx > 0 && ny > 0 && ux > 0 && uy > 0 && nx <= X && ny <= Y && ux <= X && uy <= Y && mas[ny][nx] != 1 && mas[uy][ux] != 1 && d[nx][ny][ux][uy] == 0){
	que.push(P(nx,ny,ux,uy,p.cost++));
	d[nx][ny][ux][uy] =  1;
      }
      else if((nx <= 0 || nx > X || ny <= 0 || ny > Y || mas[ny][nx] == 1) && ux <= X && uy <= Y && ux > 0 && uy > 0 && mas[uy][ux] != 1 && d[nx][ny][ux][uy] == 0){
	que.push(P(p.tx,p.ty,ux,uy,p.cost++));
	d[p.tx][p.ty][ux][uy] = 1;
      }
      else if((ux <= 0 || ux > X || uy <= 0 || uy > Y || mas[uy][ux] == 1) && nx <= X && ny <= Y && nx > 0 && ny > 0 && mas[ny][nx] != 1 && d[nx][ny][ux][uy] == 0){
	que.push(P(nx,ny,p.kx,p.ky,p.cost++));
	d[nx][ny][p.kx][p.ky] = 1;
      }
    }
  }
  return -1;
}

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

using namespace std;

typedef pair<int, int> P;
typedef pair<P, P> Q;
typedef pair<int, Q> R;

int main() {
	int x, y;
	int dx[] = {1, 0, -1, 0};
	int dy[] = {0, 1, 0, -1};
	int dx2[] = {-1, 0, 1, 0};
	int dy2[] = {0, -1, 0, 1};
	while (cin >> x >> y) {
		if (x == 0 && y == 0) {
			break;
		}
		P s1, s2;
		cin >> s1.first >> s1.second;
		cin >> s2.first >> s2.second;
		s1.first--;
		s1.second--;
		s2.first--;
		s2.second--;
		vector< vector<int> > mp(y, vector<int>(x));
		if (s1 == s2) {
			cout << 0 << endl;
		} else {
			int b;
			for (int i = 0; i < y; i++) {
				for (int j = 0; j < x; j++) {
					cin >> b;
					if (b == 1) {
						mp[i][j] = -1;
					} else {
						mp[i][j] = 0;
					}
				}
			}
			mp[s1.second][s1.first] = mp[s2.second][s2.first] = -1;
			queue<R> q;
			q.push(R(0, Q(s1, s2)));
			bool h2 = false;
			while(!q.empty()) {
				R r = q.front();
				q.pop();
				P p1 = (r.second).first;
				P p2 = (r.second).second;
				bool h = false;
				//cout << r.first+1 << endl;
				//cout << p1.first << ' ' << p1.second << endl;
				//cout << p2.first << ' ' << p2.second << endl;
				for (int i = 0; i < 4; i++) {
					if (0 <= p1.first+dx[i] && p1.first+dx[i] < x && 0 <= p1.second+dy[i] && p1.second+dy[i] < y && mp[p1.second+dy[i]][p1.first+dx[i]] == 0 &&
						0 <= p2.first+dx2[i] && p2.first+dx2[i] < x && 0 <= p2.second+dy2[i] && p2.second+dy2[i] < y && mp[p2.second+dy2[i]][p2.first+dx2[i]] == 0) {
							if ((p1.first+dx[i] == p2.first+dx2[i])&&(p1.second+dy[i] == p2.second+dy2[i])) {
								h = h2 = true;
								break;
							} else {
								R r2;
								r2.first = r.first+1;
								r2.second = Q(P(p1.first+dx[i], p1.second+dy[i]), P(p2.first+dx2[i], p2.second+dy2[i]));
								mp[p1.second+dy[i]][p1.first+dx[i]] = mp[p2.second+dy2[i]][p2.first+dx2[i]] = r2.first;
								if (r2.first >= 100) {
									h = true;
									break;
								} else {
									q.push(r2);
								}
							}
					} 
				}
				if (h) {
					if (h2) {
						cout << r.first+1 << endl;
					}
					break;
				} 
			}
			if (!h2) {
				cout << "NA" << endl;
			}
		}
	}
	return 0;
}