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>
using namespace std;

int INF=-10;

class point{
    public:
        int x,y;
};

int main(){
    while(1){
        int w,h;
        cin>>w>>h;
        if(w+h==0){
            break;
        }
        int tx,ty;
        int kx,ky;
        cin>>tx>>ty;
        cin>>kx>>ky;

        int d[60][60];
        for(int i=0;i<60;i++){
            for(int j=0;j<60;j++){
                d[i][j]=-1;
            }
        }
        for(int j=1;j<w+1;j++){
            for(int i=1;i<h+1;i++){
                cin>>d[i][j];
                if(d[i][j]==1){
                    d[i][j]=-1;
                }
                if(d[i][j]==0){
                    d[i][j]=INF;
                }
            }
        }
        queue<point> quet;
        queue<point> quek;

        point t;
        t.x=tx; t.y=ty;
        point k;
        k.x=kx; k.y=ky;

        quet.push(t);
        quek.push(k);
        d[t.x][t.y]=0;
        d[k.x][k.y]=0;

        while(!quet.empty()||!quek.empty()){
            t=quet.front(); quet.pop();
            k=quek.front(); quek.pop();

            if(t.x==k.x&&t.y==k.y){
                break;
            }

            if(d[t.x-1][t.y]==INF&&d[k.x+1][k.y]==INF&&d[t.x-1][t.y]!=-1&&d[k.x+1][k.y]!=-1){
                point t2;
                point k2;
                t2.x=t.x-1; t2.y=t.y;
                k2.x=k.x+1; k2.y=k.y;
                quet.push(t2);
                quek.push(k2);
                d[t2.x][t2.y]=d[t.x][t.y]+1;
                d[k2.x][k2.y]=d[k.x][k.y]+1;
            }
            if(d[t.x+1][t.y]==INF&&d[k.x-1][k.y]==INF&&d[t.x+1][t.y]!=-1&&d[k.x-1][k.y]!=-1){
                point t2;
                point k2;
                t2.x=t.x+1; t2.y=t.y;
                k2.x=k.x-1; k2.y=k.y;
                quet.push(t2);
                quek.push(k2);
                d[t2.x][t2.y]=d[t.x][t.y]+1;
                d[k2.x][k2.y]=d[k.x][k.y]+1;
            }
            if(d[t.x][t.y-1]==INF&&d[k.x][k.y+1]==INF&&d[t.x][t.y-1]!=-1&&d[k.x][k.y+1]!=-1){
                point t2;
                point k2;
                t2.x=t.x; t2.y=t.y-1;
                k2.x=k.x; k2.y=k.y+1;
                quet.push(t2);
                quek.push(k2);
                d[t2.x][t2.y]=d[t.x][t.y]+1;
                d[k2.x][k2.y]=d[k.x][k.y]+1;
            }
            if(d[t.x][t.y+1]==INF&&d[k.x][k.y-1]==INF&&d[t.x][t.y+1]!=-1&&d[k.x][k.y-1]!=-1){
                point t2;
                point k2;
                t2.x=t.x; t2.y=t.y+1;
                k2.x=k.x; k2.y=k.y-1;
                quet.push(t2);
                quek.push(k2);
                d[t2.x][t2.y]=d[t.x][t.y]+1;
                d[k2.x][k2.y]=d[k.x][k.y]+1;
            }
        }

        if(t.x==k.x&&t.y==k.y){
            cout<<d[t.x][t.y]<<endl;
        }else{
            cout<<"NA"<<endl;
        }
    }

    return 0;
}

C++: #include <iostream>
#include <set>
#include <queue>
#include <map>
#include <stdlib.h>

using namespace std;

struct Point{
	int tx;
	int ty;
	int kx;
	int ky;
	Point( int dtx, int dty, int dkx, int dky ){
		tx = dtx;
		ty = dty;
		kx = dkx;
		ky = dky;
	}
};

Point move( int next, const Point& point, int stage[51][51] )
{
	switch( next ){
		case 0:
			return Point( stage[point.tx + 1][point.ty] ? point.tx : point.tx + 1, point.ty, stage[point.kx - 1][point.ky] ? point.kx : point.kx - 1, point.ky );
		case 1:
			return Point( stage[point.tx - 1][point.ty] ? point.tx : point.tx - 1, point.ty, stage[point.kx + 1][point.ky] ? point.kx : point.kx + 1, point.ky );
		case 2:
			return Point( point.tx, stage[point.tx][point.ty + 1] ? point.ty : point.ty + 1, point.kx, stage[point.kx][point.ky - 1] ? point.ky : point.ky - 1);
		case 3:
			return Point( point.tx, stage[point.tx][point.ty - 1] ? point.ty : point.ty - 1, point.kx, stage[point.kx][point.ky + 1] ? point.ky : point.ky + 1);
	}

	return Point(1,1,1,1);
}
	

int change( const Point& data )
{
	return data.tx + data.ty * 51 + data.kx * 51 * 51 + data.ky * 51 * 51 * 51;
}

int bfs( const Point& start, int stage[51][51] )
{
	set<int> history;
	queue<Point> q;
	map<int,int> dist;

	dist[change( start )] = 0;
	history.insert( change( start ) );

	q.push( start );
	while( !q.empty() ){
		Point u = q.front();
		if( u.tx == u.kx && u.ty == u.ky ) return dist[change( u )];

		for( int i = 0;i < 4;i++ ){
			Point v = move( i, u, stage );
			if( history.count( change( v ) ) ) continue;
			dist[change( v )] = dist[change( u )] + 1;
			history.insert( change( v ) );
			q.push( v );
		}

		q.pop();
	}
	return -1;
}
int main(int argc, char const* argv[])
{
	int X,Y;
	Point point(0,0,0,0);
	int stage[51][51];

	while( cin >> X >> Y && X != 0 ){
		cin >> point.tx >> point.ty;
		cin >> point.kx >> point.ky;
		for( int i = 0;i < 51;i++ ){
			for( int j = 0;j < 51;j++ ){
				stage[i][j] = 1;
			}
		}

		for( int i = 1;i <= Y;i++ ){
			for( int j = 1;j <= X;j++ ){
				cin >> stage[j][i];
			}
		}

		int answer = bfs( point, stage );
		if( answer == -1 ) cout << "NA" << endl;
		else cout << answer << endl;
	}

	return 0;
}