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)
	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 pq.Len() > 0 {
		//now := heap.Pop(&pq).(*Status)
		//now := pq.Pop().(*Status)
		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 += 1
			if next.Turn <= 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				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 <stdio.h>
#include <cctype>
#include <limits.h>
#include <math.h>
#include <complex>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <cstring>
#include <string>
#include <sstream>
#include <algorithm>
#include <iomanip>
#include <iostream>

#define VARIABLE(x) cerr << #x << "=" << x << endl
#define BINARY(x) static_cast<bitset<16> >(x);
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define REP(i,m,n) for (int i=m;i<(int)(n);i++)
#define if_range(x, y, w, h) if (0<=(int)(x) && (int)(x)<(int)(w) && 0<=(int)(y) && (int)(y)<(int)(h))

const int INF = 1000000000;
const double EPS = 1e-8;
const double PI = 3.14159;
int dx[4]={0, 1, 0, -1}, dy[4]={-1, 0, 1, 0};
using namespace std;
//typedef pair<int, int> P;
struct P {
	int x, y;
	P(int x, int y):x(x), y(y){}
	P(){}
};

struct PP {
	P a, b;
	int time;
	PP(P a, P b, int t) : a(a), b(b), time(t) {}
	PP() {}
};

/** Problem0223 : Stray Twins **/
int main()
{
	int W, H;
	while (cin>>W>>H, W||H) {
		bool wall[W][H];
		int tx, ty, kx, ky;
		cin>>tx>>ty>>kx>>ky;
		tx--, ty--, kx--, ky--;
		
		rep(y, H) rep(x, W) cin>>wall[x][y];
		
		queue<PP> Q;
		
		bool vis[51][51][51][51] = {0};
		Q.push(PP(P(tx, ty), P(kx, ky), 0));
		vis[tx][ty][kx][ky] = true;
		
		while (Q.size()) {
			PP pp = Q.front(); Q.pop();
//			cerr << pp.a.x << " " << pp.a.y << " " << pp.b.x << " " << pp.b.y << endl;
			
			if (pp.time > 100) continue;
			if (pp.a.x == pp.b.x && pp.a.y == pp.b.y) {
				cout << pp.time << endl;
				goto end;
			}
			
			rep(i, 4) {
				PP np = pp;
				np.a.x += dx[i];
				np.b.x -= dx[i];
				np.a.y += dy[i];
				np.b.y -= dy[i];
				np.time++;
				
				if_range(np.a.x, np.a.y, W, H) {
					if (!wall[np.a.x][np.a.y])
						;
					else
						np.a = pp.a;
				} else np.a = pp.a;
				
				if_range(np.b.x, np.b.y, W, H) {
					if (!wall[np.b.x][np.b.y])
						;
					else
						np.b = pp.b;
				} else np.b = pp.b;
				
				if (!vis[np.a.x][np.a.y][np.b.x][np.b.y]) {
					vis[np.a.x][np.a.y][np.b.x][np.b.y] = true;
					Q.push(np);
				}
			}
		}
		
		cout << "NA" << endl;
	end:;
	}
}

C++: #include <cstdio>
#include <queue>
#include <map>
#include <utility>

using namespace std;

typedef pair<int,int> P1;
typedef pair<P1,P1> P2;
typedef pair<P2,int> P;

#define CHECK(X,Y) (0<=(X)&&(X)<(Y))

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

int main() {
	int X,Y;
	int tx,ty;
	int kx,ky;
	int d[50][50];
	while(scanf("%d %d",&X,&Y),X||Y) {
		scanf("%d %d",&tx,&ty);
		scanf("%d %d",&kx,&ky);
		for(int j=0;j<Y;j++) {
			for(int i=0;i<X;i++) {
				scanf("%d",&d[i][j]);
			}
		}
		queue<P> que;
		map<P2,bool> mp;
		que.push(P(P2(P1(tx-1,ty-1),P1(kx-1,ky-1)),0));
		bool na=true;
		while(!que.empty()) {
			P p=que.front();que.pop();
			tx=p.first.first.first,ty=p.first.first.second;
			kx=p.first.second.first,ky=p.first.second.second;
			if(p.second>=100) break;
			if(tx==kx&&ty==ky) {
				na=false;
				printf("%d\n",p.second);
				break;
			}
			mp[p.first]=true;
			for(int i=0;i<4;i++) {
				int ntx=tx,nty=ty,nkx=kx,nky=ky;
				if(CHECK(ntx+dx[i],X)&&CHECK(nty+dy[i],Y)&&!d[ntx+dx[i]][nty+dy[i]]) ntx+=dx[i],nty+=dy[i];
				if(CHECK(nkx-dx[i],X)&&CHECK(nky-dy[i],Y)&&!d[nkx-dx[i]][nky-dy[i]]) nkx-=dx[i],nky-=dy[i];
				P2 p2(P1(ntx,nty),P1(nkx,nky));
				if(mp.find(p2)==mp.end()) {
					que.push(P(p2,p.second+1));
				}
			}
		}
		if(na) printf("NA\n");
	}
}