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 <queue>
#include <cstring>

using namespace std;
struct PointPair {
        int step;
        int tx, ty, kx, ky;
};

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

bool passed[50][50][50][50];
bool field[50][50];

int main(){
        while(true){
                memset(passed, 0, sizeof(passed));
                memset(field, 0, sizeof(field));
                int X, Y, tx, ty, kx, ky;
                cin >> X >> Y;
                if(X == 0 || Y == 0){ break; }
                cin >> tx >> ty >> kx >> ky;
                for(int i = 0; i < Y; ++i){
                        for(int j = 0; j < X; ++j){
                                int f;
                                cin >> f;
                                field[i][j] = (f != 0);
                        }
                }
                --tx; --ty; --kx; --ky;
                PointPair init = { 0, tx, ty, kx, ky };
                queue<PointPair> q;
                q.push(init);
                passed[tx][ty][kx][ky] = true;
                int answer = -1;
                while(!q.empty()){
                        PointPair p = q.front();
                        if(p.step >= 100){ break; }
                        if(p.tx == p.kx && p.ty == p.ky){
                                answer = p.step;
                                break;
                        }
                        q.pop();
                        for(int i = 0; i < 4; ++i){
                                PointPair next;
                                next.step = p.step + 1;
                                next.tx = p.tx + dx[i];
                                next.ty = p.ty + dy[i];
                                if(
                                        field[next.ty][next.tx] ||
                                        next.tx < 0 || next.tx >= X ||
                                        next.ty < 0 || next.ty >= Y
                                ){
                                        next.tx = p.tx;
                                        next.ty = p.ty;
                                }
                                next.kx = p.kx - dx[i];
                                next.ky = p.ky - dy[i];
                                if(
                                        field[next.ky][next.kx] ||
                                        next.kx < 0 || next.kx >= X ||
                                        next.ky < 0 || next.ky >= Y
                                ){
                                        next.kx = p.kx;
                                        next.ky = p.ky;
                                }
                                if(!passed[next.tx][next.ty][next.kx][next.ky]){
                                        passed[next.tx][next.ty][next.kx][next.ky] = true;
                                        q.push(next);
                                }
                        }
                }
                if(answer < 0){
                        cout << "NA" << endl;
                }else{
                        cout << answer << endl;
                }
        }
        return 0;
}

C++: #include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define RFOR(i,a,b) for(int i=(b) - 1;i>=(a);i--)
#define REP(i,n) for(int i=0;i<(n);i++)
#define RREP(i,n) for(int i=n-1;i>=0;i--)

#define PB push_back
#define INF INT_MAX/3
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define CLR(a) memset(a,0,sizeof(a))

typedef long long int ll;

using namespace std;
int dx[] = {-1,0,0,1};
int dy[] = {0,1,-1,0};
int xs,ys,tx,ty,kx,ky;


int main(){
    while(true){
	cin >> xs >> ys;
	if(xs == 0 && ys == 0) break;
	cin >> tx >> ty;
	cin >> kx >> ky;
	tx--;
	ty--;
	kx--;
	ky--;
	vector< vector<int> > map(ys,vector<int>(xs));
	REP(i,ys)REP(j,xs) cin >> map[i][j];

	queue<int> qtx;
	queue<int> qty;
	queue<int> qkx;
	queue<int> qky;
	queue<int> qn;
	vector< vector<bool> > tu(ys,vector<bool>(xs,false));
	vector< vector<bool> > ku(ys,vector<bool>(xs,false));
	int t,k;
	int ans = 10000000;
	qtx.push(tx);
	qty.push(ty);
	qkx.push(kx);
	qky.push(ky);
	qn.push(1);
	while(!qtx.empty()){
	    int x1 = qtx.front();
	    int y1 = qty.front();
	    int x2 = qkx.front();
	    int y2 = qky.front();
	    int n = qn.front();
	    if(n >= 100){
		ans = 100;
		break;
	    }
	    qtx.pop();
	    qty.pop();
	    qkx.pop();
	    qky.pop();
	    qn.pop();
	    REP(i,4){
		int ntx = x1 + dx[i];
		int nty = y1 + dy[i];
		int nkx = x2 - dx[i];
		int nky = y2 - dy[i];
		if(ntx<0 || xs <= ntx) ntx = x1;
		if(nty<0 || ys <= nty) nty = y1;
		if(nkx<0 || xs <= nkx) nkx = x2;
		if(nky<0 || ys <= nky) nky = y2;
		if(map[nty][ntx] == 1) {
		    ntx = x1;
		    nty = y1;
		}
		if(map[nky][nkx] == 1) {
		    nkx = x2;
		    nky = y2;
		}
		if(tu[nty][ntx] && ku[nky][nkx]) continue;
		tu[nty][ntx] = true;
		ku[nky][nkx] = true;
		if(ntx==nkx&&nty==nky){
		    ans = min(ans,n);
		}
		qtx.push(ntx);
		qty.push(nty);
		qkx.push(nkx);
		qky.push(nky);
		qn.push(n+1);
	    }
	}
	if(ans>=100) cout << "NA" << endl;
	else cout << ans << endl;
    }
    return 0;
}