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 := pq[0]
		pq = pq[1:]
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if ans <= now.Turn {
			continue
		}

		if _, ok := memo[now.Person]; ok {
			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++
			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<bits/stdc++.h>
#define r(i,n) for(int i=0;i<n;i++)
using namespace std;
#define mk make_pair
#define f first
#define s second
typedef pair<int,int> P;
int a[51][51],ax,bx,ay,by;
int dx1[]={1,0,-1,0};
int dy1[]={0,1,0,-1};
int dx2[]={-1,0,1,0};
int dy2[]={0,-1,0,1};
bool used[10000000];
int gethash(P q,P w){
  return q.f+q.s*52+w.f*52*52+w.s*52*52*52;
}
int main(){
  int w,h;
  while(cin>>w>>h,w){
    memset(used,0,sizeof(used));
    cin>>ax>>ay>>bx>>by;ax--,ay--,bx--,by--;
    r(i,h)r(j,w)cin>>a[i][j];
    used[gethash(P(ay,ax),P(by,bx))]=1;
    queue<pair<int,pair<pair<int,int>,pair<int,int> > > >q;
    q.push(mk(0,mk(mk(ay,ax),mk(by,bx))));
    while(!q.empty()){
      pair<int,pair<pair<int,int>,pair<int,int> > >p=q.front();q.pop();
      P p1=p.s.f,p2=p.s.s;
      if(p1==p2){
	cout<<p.f<<endl;
	goto L;
      }
      r(i,4){
	int x1=p1.s+dx1[i],x2=p2.s+dx2[i],y1=p1.f+dy1[i],y2=p2.f+dy2[i];
	if(x1<0||x1>=w)x1=p1.s;
	if(x2<0||x2>=w)x2=p2.s;
	if(y1<0||y1>=h)y1=p1.f;
	if(y2<0||y2>=h)y2=p2.f;
	if(a[y1][x1])x1=p1.s,y1=p1.f;
	if(a[y2][x2])x2=p2.s,y2=p2.f;
	if(!used[gethash(P(y1,x1),P(y2,x2))]){
	  used[gethash(P(y1,x1),P(y2,x2))]=1;
	  q.push(mk(p.f+1,mk(mk(y1,x1),mk(y2,x2))));
	}
      }
    }
    cout<<"NA"<<endl;L:;
  }
}

C++: /*??£?¨?*/
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<math.h>
#include<queue>
#include<string.h>
#include<string>
#include<vector>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
struct X
{
	int tx, ty, t, kx, ky;
};
int java[51][51][51][51] = { 0 };
int main()
{
	int w, h, map[52][52] = { 0 };
		int mx[4] = { 0,1,0,-1 }, my[4] = { 1,0,-1,0 };
		while (1)
		{
			queue<X> que;
			X c;
			cin >> w >> h;
			if (w == 0 && h == 0)
				break;
			memset(java, 0, sizeof(java));
			cin >> c.tx >> c.ty >> c.kx >> c.ky;
			c.t = 0;
			que.push(c);
			rep1(i, h)
			{
				rep1(j, w)
				{
					cin >> map[i][j];
				}
			}
			/*?£???????*/
			rep(i, h + 2)//n???????????°,m????¨??????°
			{
				map[i][0] = 1;
				map[i][w + 1] = 1;
			}
			rep(i, w + 2)
			{
				map[0][i] = 1;
				map[h + 1][i] = 1;
			}
			while (!que.empty())
			{
				c = que.front();
				que.pop();
				java[c.tx][c.ty][c.kx][c.ky] = 1;
				if (c.tx == c.kx&&c.ty == c.ky||c.t >= 100)
				{
					break;
				}
				c.t++;
				rep(i, 4)
				{
					if (java[c.tx + mx[i]][c.ty + my[i]][c.kx - mx[i]][c.ky - my[i]] == 0 && map[c.tx + mx[i]][c.ty + my[i]] == 0 && map[c.kx - mx[i]][c.ky - my[i]] == 0)
					{
						c.tx += mx[i];
						c.ty += my[i];
						c.kx -= mx[i];
						c.ky -= my[i];
						que.push(c);
						java[c.tx][c.ty][c.kx][c.ky] = 1;
						c.tx -= mx[i];
						c.ty -= my[i];
						c.kx += mx[i];
						c.ky += my[i];
					}
					else if (java[c.tx][c.ty][c.kx - mx[i]][c.ky - my[i]] == 0 && map[c.tx + mx[i]][c.ty + my[i]] != 0 && map[c.kx - mx[i]][c.ky - my[i]] == 0)
					{
						c.kx -= mx[i];
						c.ky -= my[i];
						que.push(c);
						java[c.tx][c.ty][c.kx][c.ky] = 1;
						c.kx += mx[i];
						c.ky += my[i];
					}
					else if (java[c.tx + mx[i]][c.ty + my[i]][c.kx][c.ky] == 0 && map[c.tx + mx[i]][c.ty + my[i]] == 0 && map[c.kx - mx[i]][c.ky - my[i]] != 0)
					{
						c.tx += mx[i];
						c.ty += my[i];
						que.push(c);
						java[c.tx][c.ty][c.kx][c.ky] = 1;
						c.tx -= mx[i];
						c.ty -= my[i];
					}
				}
			}
			if (c.tx == c.kx&&c.ty == c.ky)
				cout << c.t << endl;
			else
				cout << "NA" << endl;
		}
	return 0;
}

C++: #include<cstdio>
#include<iostream>
#include<string>
#include<map>
#include<queue>
#include<set>

using namespace std;

#define rep(i,n) for(int i=0;i<n;i++)
#define reps(i,n) for(int i=1;i<=n;i++)

class S{
	public:
	char a,b,c,d;
	int val;
	S(int a,int b,int c,int d,int val):
	a(a),b(b),c(c),d(d),val(val){}
};

char ch[55][55][55][55];

int main(){
	while(1){
		int n,m;
		cin>>n>>m;
		if(n==0)break;
		
		int sa,sb,sc,sd;
		cin>>sa>>sb>>sc>>sd;
		
		int masu[55][55]={0};
		reps(i,n){
			reps(j,m){
				cin>>masu[i][j];
			}
		}
		
		rep(i,55)rep(j,55)rep(k,55)rep(p,55)ch[i][j][k][p]=0;
		
		queue<S> que;
		que.push(S(sb,sa,sd,sc,0));
		
		int dx[4]={-1,0,1,0};
		int dy[4]={0,1,0,-1};
		
		int ans=-1;
		while(1){
			if(que.empty())break;
			
			S u = que.front();
			que.pop();
			
			
			if(u.a<=0 || u.b<=0 || u.c<=0 || u.d<=0)continue;
			if(u.a>m || u.c>m || u.b>n || u.d>n)continue;
			
			if(ch[u.a][u.b][u.c][u.d]==1)continue;
			ch[u.a][u.b][u.c][u.d]=1;
			
			//printf("%d %d  %d %d  %d\n",u.a,u.b,u.c,u.d,u.val);
			
			if(masu[u.a][u.b]==1 || masu[u.c][u.d]==1)continue;
			
			if(u.a == u.c && u.b==u.d){
				ans = u.val;
				break;
			}
			
			S e = u;
			e.val++;
			rep(i,4){
				e.a += dx[i];
				e.b += dy[i];
				e.c -= dx[i];
				e.d -= dy[i];
					
				que.push(e);
				
				e.c += dx[i];
				e.d += dy[i];
				e.a -= dx[i];
				e.b -= dy[i];
			}
		}
		if(ans==-1){
			puts("NA");
		}else
		printf("%d\n",ans);
	}
}