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<bits/stdc++.h>
using namespace std;
#define fi first
#define sc second
#define pb push_back
typedef pair<int,int> P;
typedef pair<P,P> PP;
typedef pair<int,PP> PPP;
int dx[4]={-1,0,0,1};
int dy[4]={0,-1,1,0};
int S[51][51][51][51];
int S1[51][51][51][51];
vector<PP>Now[101];
int main()
{
	while(true){
		int X,Y;
		int tx;int ty;
		int kx;int ky;
		scanf("%d%d",&X,&Y);
		if(X==0&&Y==0)break;
		scanf("%d%d%d%d",&tx,&ty,&kx,&ky);tx--;ty--;kx--;ky--;
		int grid[51][51];
		for(int i=0;i<Y;i++){
			for(int j=0;j<X;j++){
				scanf("%d",&grid[i][j]);
			}
		}
		
		for(int i=0;i<Y;i++){
			for(int j=0;j<X;j++){
				for(int k=0;k<Y;k++){
					for(int l=0;l<X;l++){
						S[i][j][k][l]=1001;
						S1[i][j][k][l]=1001;
					}
				}
			}
		}
		
		
		PP x;
		x.fi.sc=tx;x.fi.fi=ty;x.sc.sc=kx;x.sc.fi=ky;
		Now[0].pb(x);
		int ans=1001;
		bool F=true;
		for(int i=0;i<100;i++){
			for(int j=0;F&&(j<(int)Now[i].size());j++){
				PP p=Now[i][j];
				if(S[p.fi.fi][p.fi.sc][p.sc.fi][p.sc.sc]<=i)continue;
				S[p.fi.fi][p.fi.sc][p.sc.fi][p.sc.sc]=i;
				
				if(p.fi.fi==p.sc.fi&&p.fi.sc==p.sc.sc){
					ans=i;
					F=false;
				}
				for(int k=0;k<4;k++){
					PP t;
					if(p.fi.fi+dy[k]<0||p.fi.fi+dy[k]>=Y||p.fi.sc+dx[k]<0||p.fi.sc+dx[k]>=X){
						t.fi.fi=p.fi.fi;t.fi.sc=p.fi.sc;
					}
					else if(grid[p.fi.fi+dy[k]][p.fi.sc+dx[k]]==1){
						t.fi.fi=p.fi.fi;t.fi.sc=p.fi.sc;
					}
					else{
						t.fi.fi=p.fi.fi+dy[k];
						t.fi.sc=p.fi.sc+dx[k];
					}
					if(p.sc.fi-dy[k]<0||p.sc.fi-dy[k]>=Y||p.sc.sc-dx[k]<0||p.sc.sc-dx[k]>=X){
						t.sc.fi=p.sc.fi;t.sc.sc=p.sc.sc;
					}
					else if(grid[p.sc.fi-dy[k]][p.sc.sc-dx[k]]==1){
						t.sc.fi=p.sc.fi;t.sc.sc=p.sc.sc;
					}
					else{
						t.sc.fi=p.sc.fi-dy[k];
						t.sc.sc=p.sc.sc-dx[k];
					}
					if(S[t.fi.fi][t.fi.sc][t.sc.fi][t.sc.sc]<=i)continue;
					//if(i==1)printf("%d %d %d %d\n",t.fi.fi,t.fi.sc,t.sc.fi,t.sc.sc);
					Now[i+1].pb(t);
				}
			}
			Now[i].clear();
		}
		int i=100;
		for(int j=0;j<(int)Now[i].size();j++){
			if(Now[i][j].fi.fi==Now[i][j].sc.fi&&Now[i][j].fi.sc==Now[i][j].sc.sc){
				ans=100;
			}
		}
		Now[101].clear();
		if(ans==1001)printf("NA\n");
		else printf("%d\n",ans);
		
	}
	return 0;
}

C++: #include <iostream>
#include <cstring>
#include <queue>
#include <map>
#define fr first
#define sc second
using namespace std;

typedef pair<int, int> iP;
typedef pair<iP, iP> iiP;
typedef pair<iiP, int> iiiP;

int w, h;
iP ts, ks;
int mas[51][51], used[51][51][51][51];
int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};

int bfs(){
  
  memset(used, -1, sizeof(used));
  queue <iiiP> que;
  que.push(iiiP(iiP(ts, ks), 0)); used[ts.fr][ts.sc][ks.fr][ks.sc] = 0;
  while(!que.empty()){
    iiiP p = que.front(); que.pop();
    if(p.fr.fr == p.fr.sc){
      if(p.sc >= 100) return -1;
      else return p.sc;
    }
    int judge = 0;
    int tx = p.fr.fr.fr, ty = p.fr.fr.sc, kx = p.fr.sc.fr, ky = p.fr.sc.sc;
    for(int i = 0; i < 4; i++){
      int ntx = tx + dx[i], nty = ty + dy[i];
      int nkx = kx - dx[i], nky = ky - dy[i];
      if(mas[nty][ntx] == 1) ntx = tx, nty = ty;
      if(mas[nky][ntx] == 1) nkx = kx, nky = ky;

      
      if(ntx >= 0 && ntx < w && nty >= 0 && nty < h && nkx >= 0 && nkx < w && nky >= 0 && nky < h && 
	 used[ntx][nty][nkx][nky] < used[tx][ty][kx][ky] + 1){
	if(~used[ntx][nty][nkx][nky]) continue;
	que.push(iiiP(iiP(iP(ntx, nty), iP(nkx, nky)), p.sc + 1));
	used[ntx][nty][nkx][nky] = used[tx][ty][kx][ky] + 1;
      }
    }
  }
  return -1;

}  

int main(){
  
  while(cin >> w >> h, w||h){
    cin >> ts.fr >> ts.sc;
    cin >> ks.fr >> ks.sc;
    for(int i = 0; i < h; i++){
      for(int j = 0; j < w; j++) cin >> mas[i][j];
    }

    int ans = bfs();
    if(ans == -1) cout << "NA" << endl;
    else cout << ans << endl;
  }

}