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 := pq[0]
		pq = pq[1:]
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if ans <= now.Turn {
			continue
		}

		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = 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 <vector>
#include <queue>
using namespace std;

struct papa{
    int tx,ty,kx,ky;
    papa(int ttx,int tty,int kkx,int kky){
        tx=ttx;ty=tty;kx=kkx;ky=kky;
    }
    papa(){}
};
int main(){
    int X,Y,TX,TY,KX,KY;
    int is[50][50];
    int ve[4][2][2]={{{0,1},{0,-1}},{{0,-1},{0,1}},{{1,0},{-1,0}},{{-1,0},{1,0}}};
    bool isvis[50][50][50][50];
    for(;;){
        scanf("%d%d",&X,&Y);
        if(X==0&&Y==0) break;
        scanf("%d%d%d%d",&TX,&TY,&KX,&KY);
        TX--;TY--;KX--;KY--;
        for(int i=0;i<X;i++){
            for(int j=0;j<Y;j++){
                scanf("%d",&is[i][j]);
            }
        }
        for(int i=0;i<X;i++){
            for(int j=0;j<Y;j++){
                for(int ii=0;ii<X;ii++){
                    for(int jj=0;jj<Y;jj++){
                        isvis[i][j][ii][jj]=false;
                    }
                }
            }
        }
        queue<papa> q;
        q.push(papa(TX,TY,KX,KY));
        int mi=-1;
        for(int i=1;i<100;i++){
            int sz=q.size();
            for(int j=0;j<sz;j++){
                papa now=q.front();
                q.pop();
                if(isvis[now.tx][now.ty][now.kx][now.ky]) continue;
                isvis[now.tx][now.ty][now.kx][now.ky]=true;
                for(int v=0;v<4;v++){
                    int netx=now.tx+ve[v][0][0],nety=now.ty+ve[v][0][1],nekx=now.kx+ve[v][1][0],neky=now.ky+ve[v][1][1];
                    papa p;
                    if(0<=netx&&netx<X&&0<=nety&&nety<Y&&is[netx][nety]==0){
                        p.tx=netx;
                        p.ty=nety;
                    }else{
                        p.tx=now.tx;
                        p.ty=now.ty;
                    }
                    if(0<=nekx&&nekx<X&&0<=neky&&neky<Y&&is[nekx][neky]==0){
                        p.kx=nekx;
                        p.ky=neky;
                    }else{
                        p.kx=now.kx;
                        p.ky=now.ky;
                    }
                    if(p.tx==p.kx&&p.ty==p.ky&&mi==-1) mi=i;
                    q.push(p);
                }
            }
        }
        if(mi!=-1) printf("%d\n",mi);
        else printf("NA\n");
    }
}