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)
	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)
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if v, ok := memo[now.Person]; ok && v <= now.Turn {
			continue
		}
		if ans<=now.Turn {
			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)
			}
		}
	}
	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>
#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)||!pos(nkx,nky)||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;
      }
}

C++: #include <cstdio>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <utility>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <functional>
#include <sstream>

using namespace std;

#define fst first
#define scd second
#define pb push_back
#define mp make_pair
#define chmin(a,b) a=min(a,b)
#define chmax(a,b) a=max(a,b)
#define rep(i,x) for(int i=0;i<(int)x;++i)
#define rep1(i,x) for(int i=1;i<=(int)x;++i)
#define rrep(i,x) for(int i=(int)x-1;i>=0;--i)
#define rrep1(i,x) for(int i=(int)x;i>=1;--i)
#define repf(i,a,x) for(int i=a;i<(int)x;++i)
#define repf1(i,a,x) for(int i=a;i<=(int)x;++i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()

template<typename T> T get(){T a;cin >> a;return a;}
template<typename T> T rev(T & a){reverse(all(a));return a;}

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

const int inf = 1e9;
const ll linf = 1e18;

class P {
public:
    int x, y;
    P () {
        x = y = 0;
    };
    P (int x0,int y0) {
        x=x0,y=y0;
    };
};

int dx[4] = {-1, 0, 0, 1}, dy[4] = {0, -1, 1, 0};

int d[52][52];
int memo[52][52][52][52];
bool used[52][52][52][52];

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int X, Y;
    while (cin >> X >> Y, X || Y) {
        int tx, ty; cin >> tx >> ty;
        int kx, ky; cin >> kx >> ky;
        fill(d[0], d[Y+2], 1);
        rep1(i, Y) rep1(j, X) cin >> d[i][j];

        queue<pair<P, P> > q;

        q.push(mp(P(tx, ty), P(kx, ky)));
        memo[ty][tx][ky][kx] = 0;

        while (q.size()) {
            pair<P, P> r = q.front(); q.pop();
            P f = r.fst, s = r.scd;

            if (f.x == s.x && f.y == s.y) {
                cout << memo[f.y][f.x][s.y][s.x] << endl;
                goto nxt;
            }
            if (memo[f.y][f.x][s.y][s.x] >= 100) continue;
            if (used[f.y][f.x][s.y][s.x]) continue;
            used[f.y][f.x][s.y][s.x] = true;

            rep(i, 4) {
                int nfx = f.x + dx[i], nfy = f.y + dy[i];
                int nsx = s.x - dx[i], nsy = s.y - dy[i];
                if (d[nfy][nfx] == 1 && d[nsy][nsx] == 1) continue;
                if (d[nfy][nfx] == 1) nfx -= dx[i], nfy -= dy[i];
                if (d[nsy][nsx] == 1) nsx += dx[i], nsy += dy[i];
                memo[nfy][nfx][nsy][nsx] = memo[f.y][f.x][s.y][s.x] + 1;
                q.push(mp(P(nfx, nfy), P(nsx, nsy)));
            }
        }

        cout << "NA" << endl;

nxt:;
    }
}