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 <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstring>
#include <sstream>
using namespace std;
static const double EPS = 1e-5;
typedef long long ll;
typedef pair<int,int> pi;
#define rep(i,n) for(int i=0;i<n;i++)


int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};
bool past[50][50][50][50];
int d[50][50];
int x,y;
int tx,ty,kx,ky;


main(){
	while(cin>>x>>y,x){
		cin>>tx>>ty>>kx>>ky;
		--tx;
		--ty;
		--kx;
		--ky;
		memset(d,0,sizeof(d));
		rep(i,x)rep(j,y)cin>>d[i][j];
		
		queue<pair<pair<pi,pi>,int> > state;
		memset(past,0,sizeof(past));
		
		state.push(make_pair(make_pair(make_pair(tx,ty),make_pair(kx,ky)),0));
		
		past[tx][ty][kx][ky]=1;
		
		int time=0;
		bool na=true;
		
		while(!state.empty()){
			pair<pi,pi> tp=state.front().first;
			time=state.front().second;
			state.pop();
			if(time>=100)break;
			if(tp.first==tp.second){
				na=false;
				break;
			}
			
			rep(i,4){
				int ttx=tp.first.first+dx[i],tty=tp.first.second+dy[i],
					tkx=tp.second.first-dx[i],tky=tp.second.second-dy[i];
				
				if(ttx<0 || ttx>=x || tty<0 || tty>=y || d[ttx][tty]==1){
					ttx-=dx[i];
					tty-=dy[i];
				}
				if(tkx<0 || tkx>=x || tky<0 || tky>=y || d[tkx][tky]==1){
					tkx+=dx[i];
					tky+=dy[i];
				}
				pair<pair<int,int>,pair<int,int> > next=make_pair(make_pair(ttx,tty),make_pair(tkx,tky));
				
				if(past[ttx][tty][tkx][tky])continue;
				past[ttx][tty][tkx][tky]=1;
				state.push(make_pair(next,time+1));
			}
		}
		
		if(na)puts("NA");
		else cout<<time<<endl;
	}
}

C++: #include <iostream>
#include <queue>
#define rep2(x,from,to) for(int x=(from);(x)<(to);(x)++)
#define rep(x,to) rep2(x,0,to)
using namespace std;
bool mem[52][52][52][52] = {{{{}}}};
struct S{
	int a,b,c,d,t;
};
int dx[4] = {-1,0,1,0};
int dy[4] = {0,1,0,-1};
void init() {
	memset(mem,0,sizeof(mem));
}
int main(){
	int x, y, tx, ty, kx, ky, k;
	while(cin >> x >> y, (x || y)) {
		int b[52][52] = {};
		init();
		cin >> tx >> ty >> kx >> ky;
		rep(i,y) {
			rep(j,x) {
				cin >> k;
				b[i+1][j+1] = 1-k;
			}
		}
		queue<S> q;
		S s = {tx,ty,kx,ky,0};
		q.push(s);
		while(!q.empty()) {
			S s = q.front();
			if(q.front().t >= 100) break;
			if(s.a==s.c&&s.b==s.d) break;
			q.pop();
			if(mem[s.a][s.b][s.c][s.d]++) continue;
			rep(i,4) {
				int na = s.a+dx[i], nb = s.b+dy[i], nc = s.c+dx[(i+2)%4], nd = s.d+dy[(i+2)%4];
				if(!b[nb][na]&&!b[nd][nc]) continue;
				if(!b[nb][na]) na = s.a, nb = s.b;
				if(!b[nd][nc]) nc = s.c, nd = s.d;
				S ns = {na, nb, nc, nd, s.t+1};
				q.push(ns);
			}
		}
		if(q.empty()) cout << "NA" << endl;
		else if(q.front().t >= 100) cout << "NA" << endl;
		else cout << q.front().t << endl;
	}
}

C++: #include <iostream>
#include <queue>
#include <algorithm>
#include <cstring>
using namespace std;

#define MAX_Y 50
#define MAX_X 50

int X, Y;
bool F[MAX_Y][MAX_X];

struct S {
    int ty, tx, ky, kx;
    int t;
    S(int ty, int tx, int ky, int kx, int t) : ty(ty), tx(tx), ky(ky), kx(kx), t(t){} 
};

const int dty[] = {0, 1, 0, -1},
          dtx[] = {1, 0, -1, 0},
          dky[] = {0, -1, 0, 1},
          dkx[] = {-1, 0, 1, 0};

bool used[MAX_Y][MAX_X][MAX_Y][MAX_X];
int bfs(int ty, int tx, int ky, int kx) {
    memset(used, 0, sizeof(used));
    queue<S> q;
    q.push(S(ty, tx, ky, kx, 0));
    while (!q.empty()) {
        S s = q.front(); q.pop();
        if (s.ty == s.ky && s.tx == s.kx) return s.t;
        if (s.t >= 100) break;
        for (int i = 0; i < 4; i++) {
            int nty = s.ty + dty[i],
                ntx = s.tx + dtx[i],
                nky = s.ky + dky[i],
                nkx = s.kx + dkx[i],
                nt  = s.t + 1;
            if (0 <= nty && nty < Y && 0 <= ntx && ntx < X) {
                if (F[nty][ntx]) {
                    nty = s.ty, ntx = s.tx;
                }
            } else {
                nty = s.ty, ntx = s.tx;
            }
            if (0 <= nky && nky < Y && 0 <= nkx && nkx < X) {
                if (F[nky][nkx]) {
                    nky = s.ky, nkx = s.kx;
                }
            } else {
                nky = s.ky, nkx = s.kx;
            }
            if (used[nty][ntx][nky][nkx]) continue;
            q.push(S(nty, ntx, nky, nkx, nt));
            used[nty][ntx][nky][nkx] = true;
        }
    }
    return -1;
}

int main() {
    while (cin >> X >> Y, X || Y) {
        int tx, ty, kx, ky;
        cin >> tx >> ty >> kx >> ky;
        ty--, tx--, ky--, kx--;
        for (int i = 0; i < Y; i++) {
            for (int j = 0; j < X; j++) {
                cin >> F[i][j];
            }
        }
        int t = bfs(ty, tx, ky, kx);
        if (t >= 0) {
            cout << t << endl;
        } else {
            cout << "NA" << endl;
        }
    }
    return 0;
}