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 <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()
#define INF 1<<30

using namespace std;

typedef long long ll;
typedef pair<int, int> P;
typedef pair<P,P> PP;
typedef pair<PP,int> PPi;

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

int grid[50][50];
bool vis[50][50][50][50];

/*
struct POS{
	int tx, ty, kx, ky, t;
	POS (int _tx, int _ty, int _kx, int _ky, int _t ) : tx(_tx), ty(_ty), kx(_kx), ky(_ky), t(_t) {}
//	bool operator>(const POS &a ) const{ return t > a.t; }
};
*/
int main()
{
//	cut here before submit 
//	freopen ("testcase.stray_twins", "r", stdin );
	int w, h;
	while (scanf ("%d %d", &w, &h ) && w && h ){
		memset (grid, 0, sizeof (grid ) );
//		memset (vis, false, sizeof (vis ) );

		rep (i, 50 ) rep (j, 50 ) rep (k, 50 ) rep (l, 50 ) vis[i][j][k][l] = false;
			
		int tx, ty;
		scanf ("%d %d", &tx, &ty );
		tx--;ty--;
		int kx, ky;
		scanf ("%d %d", &kx, &ky );
		kx--;ky--;
		rep (i, h ){
			rep (j, w ){
				scanf ("%d", &grid[i][j] );
			} // end rep
		} // end rep

		vis[tx][ty][kx][ky] = true;
//		priority_queue<POS, vector<POS>, greater<POS> > que;
		queue<PPi> que;
		que.push (PPi (PP(P (tx, ty), P(kx, ky ) ), 0 ) );
		int res = INF;
		while (!que.empty() ){
			PPi curr = que.front(); que.pop();
			int ctx = curr.first.first.first;
			int cty = curr.first.first.second;
			int ckx = curr.first.second.first;
			int cky = curr.first.second.second; 
			int ct  = curr.second;
			rep (k, 4 ){
				int ntx = ctx + dx[k]; int nty = cty + dy[k];
				int nkx = ckx - dx[k]; int nky = cky - dy[k];
				if (ntx < 0 || ntx >= w || nty < 0 || nty >= h || grid[nty][ntx] ){
					ntx = tx; nty = ty;
				} // end if
				if (nkx < 0 || nkx >= w || nky < 0 || nky >= h || grid[nky][nkx] ){
					nkx = kx; nky = ky;
				} // end if
				if (vis[ntx][nty][nkx][nky] || ct + 1 >= 100 ) continue;
				if (ntx == nkx && nty == nky ){
					res = ct+1;
					goto ans;
				} // end if
				vis[ntx][nty][nkx][nky] = true;
				que.push (PPi (PP (P (ntx, nty ), P (nkx, nky ) ), ct+1 ) );
			} // end rep
		} // end while
ans:;
		if (res != INF ){
			printf ("%d\n", res );
		}else{
			printf ("NA\n" );
		} // end if

	} // end loop
		
	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];
					
				if(masu[e.a][e.b]==1 || masu[e.c][e.d]==1){
				}else if(ch[e.a][e.b][e.c][e.d]==1){
				}else{
					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);
	}
}