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 <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <sstream>
#include <stack>
#include <queue>
#include <cstring>
#include <list>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> VI;
static const double EPS = 1e-5;
static const int INFTY = (1<<21);
static const ll LLINFTY = (1LL<<53);
#define REP(i,m,n) for(i=m;i<n;i++)
#define rep(i,n) REP(i,0,n)
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin();i!=(c).end();++i)
#define out(a,b) (a<0||a>=b)
struct node{
  int tx,ty;
  int kx,ky;
  int c;
  int mini;
  node(){}
  node(int a,int b,int c_,int d,int e):tx(a),ty(b),kx(c_),ky(d),c(e),
  mini((abs(a-c_)+abs(b-d))/2){}
  bool operator>(const node& e)const{
    return c+mini>e.c+e.mini;
  }
};
bool used[50][50][50][50];
int dx[]={0,1,0,-1};
int dy[]={0,-1,0,1};
int main(void)
{
  int w,h,i,j,ii,jj;
  int tx,ty,kx,ky;
  int g[50][50];
  node p;
  for(;;){
    scanf("%d%d",&w,&h); if(!w)break;
    scanf("%d%d%d%d",&tx,&ty,&kx,&ky); tx--; ty--; kx--; ky--;
    rep(i,h)rep(j,w){
      scanf("%d",g[i]+j);
      rep(ii,h)rep(jj,w)used[i][j][ii][jj]=false;
    }
    priority_queue<node,vector<node>,greater<node> >q;
    q.push( node(tx,ty,kx,ky,0) );
    used[ty][tx][ky][kx]=true;
    while( !q.empty() ){
      p=q.top(); q.pop();
      if(p.tx==p.kx && p.ty==p.ky){
        printf("%d\n",p.c);
        goto END;
      }
      rep(i,4){
        tx=p.tx+dx[i]; ty=p.ty+dx[3-i];
        kx=p.kx+dy[i]; ky=p.ky+dy[3-i];
        if(out(tx,w)||out(ty,h)||g[ty][tx])tx=p.tx,ty=p.ty;
        if(out(kx,w)||out(ky,h)||g[ky][kx])kx=p.kx,ky=p.ky;
        if(!used[ty][tx][ky][kx]){
          used[ty][tx][ky][kx]=true;
          q.push(node(tx,ty,kx,ky,p.c+1));
        }
      }
    }
    puts("NA");
  END:;
  }
}

C++: #include <iostream>
#include <map>
#include <queue>
#include <sstream>
#include <cmath>

using namespace std;

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

class state {
public:
    int tx, ty;
    int kx, ky;
    int time;
    state(int a, int b, int c, int d, int e) {
        tx = a;
        ty = b;
        kx = c;
        ky = d;
        time = e;
    }
};

int h, w;
int grid[55][55];
int tx, ty, kx, ky;

int dis(int x1, int y1, int x2, int y2)
{
    return abs(y2 - y1) + abs(x2 - x1);
}

void solve()
{
    int ans = -1;
    state s(tx, ty, kx, ky, 0);
    map<string, bool> m;
    queue<state> q;
    ostringstream oss;

    oss << tx << "," << ty << "," << kx << "," << ky;
    q.push(s);
    m[oss.str()] = true;

    while (!q.empty()) {
        state now = q.front();
        q.pop();

        if (now.time >= 100)
            break;
        if (now.tx == now.kx && now.ty == now.ky) {
            ans = now.time;
            break;
        }

        for (int i = 0; i < 4; i++) {
            int ntx = now.tx + dx[i];
            int nty = now.ty + dy[i];
            int nkx = now.kx + dx[(i + 2) % 4];
            int nky = now.ky + dy[(i + 2) % 4];

            if (ntx < 1 || ntx > w)
                ntx = now.tx;
            if (nty < 1 || nty > h)
                nty = now.ty;
            if (nkx < 1 || nkx > w)
                nkx = now.kx;
            if (nky < 1 || nky > h)
                nky = now.ky;
            if (grid[nty][ntx] != 0) {
                ntx = now.tx;
                nty = now.ty;
            }
            if (grid[nky][nkx] != 0) {
                nkx = now.kx;
                nky = now.ky;
            }
                
            oss.str("");
            oss << ntx << "," << nty << "," << nkx << "," << nky;

            if (m.count(oss.str()) != 0)
                continue;
            if (dis(ntx, nty, nkx, nky) > dis(now.tx, now.ty, now.kx, now.ky))
                continue;
            state next(ntx, nty, nkx, nky, now.time + 1);
            q.push(next);
            m[oss.str()] = true;
        }
    }
    if (ans == -1 || ans >= 100)
        cout << "NA" << endl;
    else
        cout << ans << endl;
}

int main()
{
    while (cin >> w >> h, w || h) {
        cin >> tx >> ty >> kx >> ky;
        for (int y = 1; y <= h; y++)
            for (int x = 1; x <= w; x++) 
                cin >> grid[y][x];
        solve();
    }

    return 0;
}