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
		}
		if ans<=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 <cstdio>
#include <cstdlib>
#include <math.h>
#include <vector>
#include <queue>
#include <algorithm>
#include <sstream>
#include <string>
using namespace std;
#define FOR(I,N) for(int I = 0; I < (int)(N); I++)
#define FIN(V) cout<<V<<endl
#define pb push_back
#define INF (1 << 30)
typedef pair<int, int> P;

int solve();
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
int w, h, tx, ty, kx, ky;
int maps[51][51];
int memo[51][51][51][51];


struct Data{
    P pt, pk;
    int cnt;
    Data(P pt_, P pk_, int cnt_){
        pt = pt_;
        pk = pk_;
        cnt = cnt_;
    }
    Data(){}
};

int main(void){
    while(cin >> w >> h, w){
        cin >> tx >> ty;
        cin >> kx >> ky;
        fill_n(*maps, 51*51, 1);
        FOR(i, h)FOR(j, w){
            cin >> maps[i+1][j+1];
        }
        int a = solve();
        if(a == -1 || a >= 100)FIN("NA");
        else FIN(a);
    }
    return 0;    
}


int solve(){
    int ans = -1;
    fill_n(***memo, 51*51*51*51, INF);
    queue<Data> que;
    que.push(Data(P(tx,ty), P(kx, ky), 0));
    while(que.size()){
        Data data = que.front();
        que.pop();
        int x1 = data.pt.first;
        int y1 = data.pt.second;
        int x2 = data.pk.first;
        int y2 = data.pk.second;
        int cost = data.cnt;
        if(cost > 100)break;
        if(memo[x1][y1][x2][y2] <= cost)continue;
        memo[x1][y1][x2][y2] = cost;
        if(x1 == x2 && y1 == y2){ans = cost;break;};
        FOR(i, 4){
            int nx1 = x1 + dx[i];
            int ny1 = y1 + dy[i];
            int nx2 = x2 - dx[i];
            int ny2 = y2 - dy[i];
            if(maps[ny1][nx1] == 1){nx1 = x1;ny1 = y1;};
            if(maps[ny2][nx2] == 1){nx2 = x2;ny2 = y2;};
            que.push(Data(P(nx1,ny1), P(nx2, ny2), cost+1));
        }
    }

    return ans;
}

C++: #include<stdio.h>
#include<iostream>
#include<queue>
#include<string.h>
using namespace std;
struct Y{
int hx,hy,rx,ry,tim;
};
int mp[52][52],c[52][52][52][52],vmp[52][52];
int main(){
int n,w,h,i,j,a[2]={1,-1},b[2],g,k;
Y e;
while(1){
queue<Y> q;
	g=0;
	k=0;
	cin>>w>>h;
	if(w==0&&h==0)break;
	cin>>e.hx>>e.hy>>e.rx>>e.ry;
	e.tim=0;
	c[e.hy][e.hx][e.ry][e.rx]=1;
	q.push(e);
	memset(mp,0,sizeof(mp));
	memset(c,0,sizeof(c));
	memset(vmp,0,sizeof(vmp));
	for(i=0;i<=h+1;i++){
		mp[i][0]=1;
		mp[i][w+1]=1;
	}
	for(i=0;i<=w+1;i++){
		mp[0][i]=1;
		mp[h+1][i]=1;
	}
	for(i=1;i<=h;i++){
		for(j=1;j<=w;j++){
			cin>>mp[j][i];
			if(mp[j][i]==1)k++;
		}
	}
	while(!q.empty()){
		e=q.front();
		q.pop();
		c[e.hy][e.hx][e.ry][e.rx]=1;
		if(vmp[e.hy][e.hx]==0){
			vmp[e.hy][e.hx]=1;
			g++;
		}
		if(vmp[e.ry][e.rx]==0){
			vmp[e.ry][e.rx]=1;
			g++;
		}
		if(e.tim>=100||e.hx==e.rx&&e.hy==e.ry||g==w*h-k)break;
		e.tim++;
		for(i=0;i<2;i++){
			if(mp[e.hy+a[i]][e.hx]!=1&&c[e.hy+a[i]][e.hx][e.ry-a[i]][e.rx]!=1&&mp[e.ry-a[i]][e.rx]!=1||c[e.hy][e.hx][e.ry-a[i]][e.rx]!=1&&mp[e.ry-a[i]][e.rx]!=1||mp[e.hy+a[i]][e.hx]!=1&&c[e.hy+a[i]][e.hx][e.ry][e.rx]!=1){
				b[0]=0;																										
				b[1]=0;																																		
				if(mp[e.hy+a[i]][e.hx]!=1){																											
					e.hy+=a[i];																																			
					b[0]=1;																																					
				}																																													
				if(mp[e.ry-a[i]][e.rx]!=1){																																										
					e.ry-=a[i];																																		
					b[1]=1;																																																														
				}																																															
				c[e.hy][e.hx][e.ry][e.rx]=1;																																		
				if(vmp[e.hy][e.hx]==0){																												
					vmp[e.hy][e.hx]=1;																																	
					g++;																																									
				}																														
				if(vmp[e.ry][e.rx]==0){																																				
					vmp[e.ry][e.rx]=1;																																					
					g++;																																													
				}																																			
				q.push(e);																											
				if(b[0]==1)e.hy-=a[i];																														
				if(b[1]==1)e.ry+=a[i];																											
			}																																																												
			if(mp[e.hy][e.hx+a[i]]!=1&&mp[e.ry][e.rx-a[i]]!=1&&c[e.hy][e.hx+a[i]][e.ry][e.rx-a[i]]!=1||mp[e.hy][e.hx+a[i]]!=1&&c[e.hy][e.hx+a[i]][e.ry][e.rx]!=1||mp[e.ry][e.rx-a[i]]!=1&&c[e.hy][e.hx][e.ry][e.rx-a[i]]!=1){
				b[0]=0;
				b[1]=0;
				if(mp[e.hy][e.hx+a[i]]!=1){
					e.hx+=a[i];
					b[0]=1;
				}
				if(mp[e.ry][e.rx-a[i]]!=1){
					e.rx-=a[i];
					b[1]=1;
				}
				c[e.hy][e.hx][e.ry][e.rx]=1;
				if(vmp[e.hy][e.hx]==0){
					vmp[e.hy][e.hx]=1;
					g++;
				}
				if(vmp[e.ry][e.rx]==0){
					vmp[e.ry][e.rx]=1;
					g++;
				}
				q.push(e);
				if(b[0]==1)e.hx-=a[i];
				if(b[1]==1)e.rx+=a[i];
			}
		}
		e.tim--;
	}
	if(e.tim>=100||q.empty()||g==w*h-k)printf("NA\n");
	else cout<<e.tim<<endl;
}
return 0;
}