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 <cstdio>
#include <vector>
#include <algorithm>
#include <complex>
#include <cstring>
#include <cstdlib>
#include <string>
#include <cmath>
#include <queue>
#include <map>
using namespace std;

#define REP(i,n) for(int i=0;i<(int)n;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
const int INF = 1<<29;

typedef pair<int,int> pii;
typedef pair<pii, pii> piiii;

int X, Y;
int ba[50][50];

int dtx[] = {0,1,0,-1};
int dty[] = {-1,0,1,0};
int dkx[] = {0,-1,0,1};
int dky[] = {1,0,-1,0};

int solve(pii T, pii K) {
  map<piiii, bool> visited;
  queue<pair<piiii, int> > Q;
  Q.push(make_pair(piiii(T,K), 0));
  while(Q.size()) {
    pii tt = Q.front().first.first, kk = Q.front().first.second;
    int m = Q.front().second;
    Q.pop();
    if (visited[piiii(tt,kk)]) continue;
    if (m >= 100) break;
    if (tt == kk) return m;
    visited[piiii(tt,kk)] = true;
//    cout << tt.first << ","<<tt.second<<" " << kk.first<<","<<kk.second << endl;
    REP(k,4) {
      int txx = tt.first + dtx[k];
      int tyy = tt.second + dty[k];
      int kxx = kk.first + dkx[k];
      int kyy = kk.second + dky[k];

      if (txx < 0 || X <= txx || tyy < 0 || Y <= tyy || ba[txx][tyy]) {
        txx -= dtx[k];
        tyy -= dty[k];
      }
      if (kxx < 0 || X <= kxx || kyy < 0 || Y <= kyy || ba[kxx][kyy]) {
        kxx -= dkx[k];
        kyy -= dky[k];
      }
      if (!visited[piiii(pii(txx, tyy),pii(kxx, kyy))])
        Q.push(make_pair(piiii(pii(txx, tyy), pii(kxx, kyy)), m+1));
    }
  }
  return -1;
}

int main() {
  while(cin >> X >> Y, X||Y) {
    int tx, ty, kx, ky;
    cin >> tx >> ty;
    cin >> kx >> ky;
    tx--;ty--;kx--;ky--;
    REP(y,Y)
      REP(x,X)
        cin >> ba[x][y];
    int res = solve(pii(tx,ty), pii(kx,ky));
    if (res < 0)
      cout << "NA" << endl;
    else
      cout << res << endl;
  }
}

C++: #include<cstring>
#include<cstdlib>
#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<stack>
using namespace std;


struct S{
  S(){};
  int tx,ty,kx,ky;
};
int X,Y;
S s;
vector<vector<int> > f;

bool input(){
  f.clear();
  s=S();
  cin>>X>>Y;
  if(X==0&&Y==0)return false;
  cin>>s.tx>>s.ty;
  cin>>s.kx>>s.ky;
  swap(s.tx,s.ty);
  swap(s.kx,s.ky);
  vector<int> kabe;
  for(int i=0;i<X+2;i++){
    kabe.push_back(1);
  }
  f.push_back(kabe);
  for(int i=0;i<Y;i++){
    vector<int> tt;
    tt.push_back(1);
    for(int j=0;j<X;j++){
      int tmp;
      cin>>tmp;
      tt.push_back(tmp);
    }
    tt.push_back(1);
    f.push_back(tt);
  }
  f.push_back(kabe);
  return true;
}

int vx[]={0,0,1,-1};
int vy[]={1,-1,0,0};
int used[60][60][60][60];
queue<S> q;
int bfs(S pos){
  memset(used,-1,(60*60*60*60));
  q = queue<S>();
  q.push(pos);
  used[pos.tx][pos.ty][pos.kx][pos.ky]=0;
  while(!q.empty()){
    S now = q.front();q.pop();
    if(used[now.tx][now.ty][now.kx][now.ky]>=100){
      return -1;
    }
    if(now.tx==now.kx&&now.ty==now.ky){
      return used[now.tx][now.ty][now.kx][now.ky];
    }
    for(int i=0;i<4;i++){
      S tmp = now;
      bool a,b;
      if(a=(f[tmp.tx+vx[i]][tmp.ty+vy[i]]!=1)){
        tmp.tx += vx[i];
        tmp.ty += vy[i];
      }
      if(b=(f[tmp.kx-vx[i]][tmp.ky-vy[i]]!=1)){
        tmp.kx -= vx[i];
        tmp.ky -= vy[i];
      }
      if( (!(a||b)) || (used[tmp.tx][tmp.ty][tmp.kx][tmp.ky]!=-1) ){
        continue;
      }
      used[tmp.tx][tmp.ty][tmp.kx][tmp.ky] = used[now.tx][now.ty][now.kx][now.ky]+1;
      if(tmp.tx==tmp.kx&&tmp.ty==tmp.ky){
        return used[tmp.tx][tmp.ty][tmp.kx][tmp.ky];
      }
      q.push(tmp);
    }
  }
  return -1;
}

int solve(){
  return bfs(s);
}

int main(){
  while(input()){
    int ans = solve();
    if(ans>=0){
      cout<<ans<<endl;
    }else{
      cout<<"NA"<<endl;
    }
  }
}

C++:   State(int a,int b,int c,int d):a(a),b(b),c(c),d(d){};
};

int h,w;
int table[51][51],memo[51][51][51][51];
int Y[4]={-1,0,1,0};
int X[4]={0,1,0,-1};

bool in(int a,int b){
  if(a<0 || b<0 || h<=a || w<=b)return false;
  return true;
}

void init(){
  for(int i=0;i<51;i++)
    for(int j=0;j<51;j++)
      for(int k=0;k<51;k++)
	for(int l=0;l<51;l++)memo[i][j][k][l]=inf;
}

int main()
{
  int a,b,c,d;
  while(1){
    cin>>w>>h;
    if(h+w==0)break;
    cin>>b>>a>>d>>c;
    a--;b--;c--;d--;
    for(int i=0;i<h;i++)for(int j=0;j<w;j++)cin>>table[i][j];
    init();

    queue<State> q;
    q.push(State(a,b,c,d));
    memo[a][b][c][d]=0;

    int ans=inf;
    while(!q.empty()){
      State u=q.front();
      q.pop();

      if(u.a==u.c && u.b==u.d){
	ans=min(memo[u.a][u.b][u.c][u.d],ans);
        continue;
      }

      if(memo[u.a][u.b][u.c][u.d]>=100)continue;

      for(int i=0;i<4;i++){
	int A=u.a+Y[i],B=u.b+X[i],C=u.c+Y[(i+2)%4],D=u.d+X[(i+2)%4];
	if(table[A][B] || !in(A,B)){
	  A=u.a;
	  B=u.b;
	}
	if(table[C][D] || !in(C,D)){
	  C=u.c;
	  D=u.d;
	}
	if(memo[A][B][C][D]>memo[u.a][u.b][u.c][u.d]+1){
	  q.push(State(A,B,C,D));
	  memo[A][B][C][D]=memo[u.a][u.b][u.c][u.d]+1;
	}
      }
    }
    if(ans>=100)cout<<"NA"<<endl;
    else cout<<ans<<endl;
  }
  return 0;
}