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 (pq PQStatus) Len() int {
	return len(pq)
}
func (pq PQStatus) Less(i, j int) bool {
	if pq[i].Turn == pq[j].Turn {
		return pq[i].Person.Distance() < pq[j].Person.Distance()
	}
	return pq[i].Turn < pq[j].Turn
}

func (pq PQStatus) Swap(i, j int) {
	pq[i], pq[j] = pq[j], pq[i]
}

func (pq *PQStatus) Push(x interface{}) {
	item := x.(*Status)
	*pq = append(*pq, item)
}

func (pq *PQStatus) Pop() interface{} {
	old := *pq
	n := len(old)
	item := old[n-1]
	*pq = old[0 : n-1]
	return item
}

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)
	//heap.Init(&pq)
	//heap.Push(&pq, start)
	//pq.Push(start)
	pq = append(pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]int64, 0)
	ans := int64(101)
	for pq.Len() > 0 {
		//now := heap.Pop(&pq).(*Status)
		//now := pq.Pop().(*Status)
		now := pq[0]
		pq = pq[1:]
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
			break
		}
		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 += 1
			if next.Turn < 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				pq = append(pq, next)
			}
		}
	}
	if ans == 101 {
		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 i=1;i<w+1;i++){
            for(int j=1;j<h+1;j++){
                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 <algorithm>
#include <queue>

using namespace std;

class State{
public:
   int x1, y1, x2, y2;
   int cost;
};

int h, w;
bool mapData[50][50];
bool visited[50][50][50][50];
int dx[] = {0, 1, 0, -1};
int dy[] = {-1, 0, 1, 0};
int ax, ay, bx, by;
int ans;

int bfs(){
   State u, v;
   u.x1 = ax-1;
   u.y1 = ay-1;
   u.x2 = bx-1;
   u.y2 = by-1;
   u.cost = 0;
   visited[u.y1][u.x1][u.y2][u.x2] = true;
   queue<State> Q;
   Q.push(u);
   while(!Q.empty()){
      u = Q.front();Q.pop();
      if(u.x1 == u.x2 && u.y1 == u.y2) return u.cost;
      for(int i=0;i<4;i++){
         int ty1 = u.y1 + dy[i];
         int tx1 = u.x1 + dx[i];
         int ty2 = u.y2 - dy[i];
         int tx2 = u.x2 - dx[i];
         if(ty1<0) ty1 = 0;
         if(tx1<0) tx1 = 0;
         if(ty2<0) ty2 = 0;
         if(tx2<0) tx2 = 0;
         if(ty1>=h) ty1 = h-1;
         if(tx1>=w) tx1 = w-1;
         if(ty2>=h) ty2 = h-1;
         if(tx2>=w) tx2 = w-1;
         if(mapData[ty1][tx1]){
            ty1 = u.y1;
            tx1 = u.x1;
         }
         if(mapData[ty2][tx2]){
            ty2 = u.y2;
            tx2 = u.x2;
         }
         if(visited[ty1][tx1][ty2][tx2]) continue;
         visited[ty1][tx1][ty2][tx2] = true;
         v.x1 = tx1;
         v.y1 = ty1;
         v.x2 = tx2;
         v.y2 = ty2;
         v.cost = u.cost+1;
         Q.push(v);
      }
   }
   return -1;
}

main(){
   while(cin >> w >> h && (h || w)){
      cin >> ax >> ay >> bx >> by;
      fill(visited[0][0][0], visited[50][0][0], false);
      for(int i=0;i<h;i++){
         for(int j=0;j<w;j++){
            cin >> mapData[i][j];
         }
      }
      ans = bfs();
      if(ans == -1) cout << "NA" << endl;
      else cout << ans << endl;
   }
   return 0;
}