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
		}
		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<bits/stdc++.h>
using namespace std;
int main(){
  int W,H;
  int counter=0;
  int vxt[4]={1,0,-1,0};
  int vyt[4]={0,-1,0,1};
  int vxk[4]={-1,0,1,0};
  int vyk[4]={0,1,0,-1};
  while(cin>>W>>H,W+H!=0){
    int tx,ty,kx,ky;
    cin>>tx>>ty;
    cin>>kx>>ky;
    int ma[H+2][W+2];
    for(int i=0;i<H+2;i++)
      for(int j=0;j<W+2;j++)
	ma[i][j]=1;
    for(int i=1;i<H+1;i++)
      for(int j=1;j<W+1;j++)
	cin>>ma[i][j];
    queue<pair<pair<int,int>,int> >T;
    queue<pair<pair<int,int>,int> >K;
    T.push(make_pair(make_pair(tx,ty),0));
    K.push(make_pair(make_pair(kx,ky),0));
    bool flag=false;
    int ans;
    while(!(T.empty())||!(K.empty())){
      if(counter>100){
	flag=true;
	break;
      }
      pair<pair<int,int>,int>nowt=T.front();
      pair<pair<int,int>,int>nowk=K.front();
      T.pop();K.pop();
      if(nowt.second==100||nowk.second==100){
	break;
      }
      if(nowt.second==nowk.second&&nowt.first.first==nowk.first.first&&
	 nowt.first.second==nowk.first.second){
	ans=nowt.second;
	flag=false;
	break;
      }
      for(int i=0;i<4;i++){
	if(ma[nowt.first.first+vxt[i]][nowt.first.second+vyt[i]]!=1)
	  T.push(make_pair(make_pair(nowt.first.first+vxt[i],nowt.first.second+vyt[i]),nowt.second+1));
	if(ma[nowk.first.first+vxk[i]][nowk.first.second+vyk[i]]!=1)
	  K.push(make_pair(make_pair(nowk.first.first+vxk[i],nowk.first.second+vyk[i]),nowk.second+1));
      }
      counter++;
    }
    if(flag)
      cout<<"NA"<<endl;
    else
      cout<<ans<<endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
#define PB push_back
#define MP make_pair
#define REP(i,n) for (int i=0;i<(n);i++)
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define ALL(a) (a).begin(),(a).end()
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
const int INF=1e9;
const int MOD=100000;
int B=1000000;
int dtx[4]={0,1,0,-1};
int dty[4]={1,0,-1,0};
int dkx[4]={0,-1,0,1};
int dky[4]={-1,0,1,0};
bool fld[50][50];
bool used[50][50][50][50];
struct A{int tx,ty,kx,ky,cnt;};
int X,Y;
bool pos(int x,int y){
      if(x<0||x>=X||y<0||y>=Y)return false;
      if(fld[x][y])return false;
      return true;
}
int main(){
      int tx,ty,kx,ky;
      while(cin>>X>>Y&&(X||Y)){
            int ans=-1;
            memset(used,false,sizeof(used));
            cin>>tx>>ty>>kx>>ky;tx--;ty--;kx--;ky--;
            REP(i,Y)REP(j,X)cin>>fld[j][i];
            queue<A>Q;
            Q.push((A){tx,ty,kx,ky,0});
            while(Q.size()){
                  A a=Q.front();Q.pop();
                  if(a.cnt>=100)continue;
                  if(a.tx==a.kx&&a.ty==a.ky){
                        ans=a.cnt;
                        break;
                  }
                  //cout<<a.tx<<" "<<a.ty<<" "<<a.cnt<<" "<<a.kx<<" "<<a.ky<<endl;
                  REP(i,4){
                        int ntx=a.tx+dtx[i],nty=a.ty+dty[i];
                        int nkx=a.kx+dkx[i],nky=a.ky+dky[i];
                        if(!pos(ntx,nty)){ntx=a.tx;nty=a.ty;}
                        if(!pos(nkx,nky)){nkx=a.kx;nky=a.ky;}
                        if(used[ntx][nty][nkx][nky])continue;
                        used[ntx][nty][nkx][nky]=true;
                        Q.push((A){ntx,nty,nkx,nky,a.cnt+1});
                  }
            }
            if(ans==-1)cout<<"NA"<<endl;
            else cout<<ans<<endl;
      }
}