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 <utility>
#include <queue>
#include <map>
using namespace std;

#define C(A,B) (0<=(A)&&(A)<(B))

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

int main() {
	int X,Y;
	int tx,ty;
	int kx,ky;
	int d[50][50];
	int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};

	while(true) {
		queue<P> que;
		map<P,int> mp;
		cin>>X>>Y;
		if(X==0&&Y==0) break;
		cin>>tx>>ty;
		cin>>kx>>ky;
		tx--;ty--;kx--;ky--;
		for(int j=0;j<Y;j++) {
			for(int i=0;i<X;i++) {
				cin>>d[i][j];
			}
		}
		P p=P(pair<int,int>(tx,ty),pair<int,int>(kx,ky));
		mp[p]=0;
		que.push(p);
		int ans=-1;
		while(que.size()) {
			P p=que.front();
			int tx=p.first.first;
			int ty=p.first.second;
			int kx=p.second.first;
			int ky=p.second.second;
			if(tx==kx&&ty==ky) {ans=mp[p];break;}
			if(mp[p]>99) break;
			for(int i=0;i<4;i++) {
				int ntx=tx,nty=ty,nkx=kx,nky=ky;
				if(C(tx+dx[i],X)&&C(ty+dy[i],Y)&&!d[tx+dx[i]][ty+dy[i]]) {
					ntx+=dx[i],nty+=dy[i];
				}
				if(C(kx-dx[i],X)&&C(ky-dy[i],Y)&&!d[kx-dx[i]][kx-dy[i]]) {
					nkx-=dx[i],nky-=dy[i];
				}
				P p2(pair<int,int>(ntx,nty),pair<int,int>(nkx,nky));
				mp[p2]=mp[p]+1;
				que.push(p2);
			}
			que.pop();
		}
		if(ans!=-1) {
			cout<<ans<<endl;
		}else {
			cout<<"NA"<<endl;
		}
	}
	return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a) (a).begin(),(a).end()
#define pb emplace_back
#define INF (1e9+1)

//verified AOJ GRL_1
#define MAX_V 2500
struct edge{int to,cost;};


void dijkstra(int s, vector<int> &d, vector<edge> G[MAX_V]){
    priority_queue< pii,vector<pii>,greater<pii> > que;
    rep( i,d.size() )d[i]=INF;
    d[s] = 0;
    que.push( pii(0,s) );
    
    while( que.size() ){
        pii p=que.top();
        que.pop();
        
        int v=p.second;
        if(d[v]<p.first)continue;
        
        rep(i,G[v].size()){
            edge e=G[v][i];
            if(d[e.to]>d[v]+e.cost){
                d[e.to]=d[v]+e.cost;
                que.push(pii(d[e.to],e.to));
            }
        }
    }
}

int w,h;
int v[51][51];

int f(int ay, int ax, int by, int bx ){
    return (ay*w+ax)*w*h + by*w+bx;
}

int main(){
    while(cin>>w>>h&&(w||h)){
        int ax,ay,bx,by;
        cin>>ax>>ay>>bx>>by;
        ax--,ay--,bx--,by--;
        
        rep(i,h)rep(j,w)cin>>v[i][j];
        
        int dy[]={1,0,-1,0};
        int dx[]={0,1,0,-1};
        
        static vector<edge> G[2500*2500+1];
        rep(i,2500*2500+1)G[i].clear();
        
        rep(ix,w){
            rep(iy,h){
                rep(jx,w){
                    rep(jy,h){
                        if(ix==jx&&iy==jy)continue;
                        rep(k,4){
                            int ddix = ix+dx[k];
                            int ddjx = jx-dx[k];
                            int ddiy = iy+dy[k];
                            int ddjy = jy-dy[k];
                            
                            if(ddiy<0 || ddiy>=h || ddix<0 || ddix>=w || v[ddiy][ddix])ddiy = iy, ddix = ix;
                            if(ddjy<0 || ddjy>=h || ddjx<0 || ddjx>=w || v[ddjy][ddjx])ddjy = jy, ddjx = jx;
                            G[f(ix,iy,jx,jy)].pb(edge{f(ddix, ddiy, ddjx, ddjy),1});
                        }
                    }
                }
            }
        }
        vector<int> d(2500*2500+1);
        dijkstra(f(ax,ay,bx,by),d,G);
        int ans = INF;
        rep(i,h){
            rep(j,w){
                if(v[i][j])continue;
                ans = min(ans,d[f(i,j,i,j)]);
            }
        }
        if(ans>=100)cout<<"NA"<<endl;
        else cout<<ans<<endl;
    }
}