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 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++
			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 <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;

        int cnt = 1;

        while (q.size()) {
            if (cnt == 100) {
                break;
            }

            queue<pair<P, P> > Q;

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

                if (used[f.y][f.x][s.y][s.x]) continue;
                used[f.y][f.x][s.y][s.x] = true;

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

                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) nfx -= dx[i], nfy -= dy[i];
                    if (d[nsy][nsx] == 1) nsx += dx[i], nsy += dy[i];
                    memo[nfy][nfx][nsy][nsx] = cnt;
                    Q.push(mp(P(nfx, nfy), P(nsx, nsy)));
                }
            }

            while (Q.size()) {
                q.push(Q.front()); Q.pop();
            }

            cnt++;
        }

        cout << "NA" << endl;

nxt:;
    }
}

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

using namespace std;

#define rep(i,j) REP((i), 0, (j))
#define REP(i,j,k) for(int i=(j);(i)<(k);++i)
#define BW(x,b) ((x)>=0&&(x)<(b))
#define Y first
#define X second
#define INF 1 << 30

typedef pair<int, int> pii;

int board[50][50], Y, X;
int dx[] = {0,1,0,-1}, dy[] = {1,0,-1,0};
bool f[51][51][51][51];

pii nextp1(pii now, int i){
  pii next = now;
  next.Y += dy[i];
  next.X += dx[i];
  //  printf("%d %d\n", next.Y, next.X);
  //  if(BW(next.Y, Y)) puts("YES");
  //  if(BW(next.X, X)) puts("YES");
  //  printf("%d\n", board[next.Y][next.X]);
  if(BW((next.Y), Y) && BW((next.X), X) && board[next.Y][next.X] == 0) return next;
  return now;
}

pii nextp2(pii now, int i){
  pii next = now;
  next.Y += -1 * dy[i];
  next.X += -1 * dx[i];
  if(BW(next.Y, Y) && BW(next.X, X) && board[next.Y][next.X] == 0) return next;
  return now;
}
     
int main(){
  while(scanf("%d%d", &X,  &Y) && X+Y){
    int tx, ty, kx, ky;
    scanf("%d%d%d%d", &tx, &ty, &kx, &ky); tx--; ty--; kx--; ky--;
    rep(i, X) rep(j, Y) scanf("%d", &board[i][j]);
    memset(f, 0, sizeof(f));

    queue<pii>tq, kq;
    tq.push(make_pair(ty, tx));
    kq.push(make_pair(ky, kx));
    f[ty][tx][ky][kx] = 1;
    int res = 1;
    while(!tq.empty()){
      //      printf("%d", res);
      int qsize = (int)tq.size();
      //      printf(" %d\n", qsize);
      rep(i, qsize){
	pii t = tq.front(); tq.pop();
	pii k = kq.front(); kq.pop();
	//	printf("%d %d %d %d\n", t.Y, t.X, k.Y, k.X);
	rep(j, 4){
	  pii nt = nextp1(t, j), nk = nextp2(k, j);
	  //	  printf("%d %d %d %d\n", nt.Y, nt.X, nk.Y, nk.X);

	  if(f[nt.Y][nt.X][nk.Y][nk.X]) continue;

	  if(nt == nk){
	    printf("%d\n", res);
	    goto end;
	  }
	  //	  fprintf(stderr, "%d %d %d %d\n", nt.Y, nt.X, nk.Y, nk.X);
	  f[nt.Y][nt.X][nk.Y][nk.X] = 1;
	  tq.push(nt); kq.push(nk);
	}
      }
      res++;
      if(res > 99) break;
    }
    //    printf("%d\n", (int)tq.size());
    puts("NA");
  end:;
  }
  return 0;
}