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 <cmath>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
#include <set>

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,j) FOR(i,0,j)
#define mp std::make_pair

typedef long long ll;
typedef unsigned long long ull;
typedef std::pair<int,int> P;
typedef std::pair<int,std::pair<P,P>> State;

const int INF = 1001001001;

// S N E W(南北東西)
const int dx[8] = {0, 0, 1, -1, 1, 1, -1, -1}, dy[8] = {1, -1, 0, 0, 1, -1, 1, -1};

int X, Y;
int tx, ty, kx, ky;
int map[50][50], d[50][50][50][50];

int main(){
    while(scanf("%d %d", &X, &Y), X || Y){
        scanf("%d %d %d %d", &tx, &ty, &kx, &ky);
        tx -= 1; ty -= 1; kx -= 1; ky -= 1;

        REP(i, Y){
            REP(j, X){
                scanf("%d", &map[i][j]);
            }
        }

        REP(i, Y){
            REP(j, X){
                REP(k, Y){
                    REP(l, X){
                        d[i][j][k][l] = INF;
                    }
                }
            }
        }

        std::queue<State> q;
        d[tx][ty][kx][ky] = 0;
        q.push(mp(0, mp(mp(tx, ty), mp(kx, ky))));

        int res = INF;
        while(!q.empty()){
            State s = q.front(); q.pop();
            int t = s.first, x1 = s.second.first.first, y1 = s.second.first.second,
                x2 = s.second.second.first, y2 = s.second.second.second;

            if(t > 100){continue;}
            if(x1 == x2 && y1 == y2){res = std::min(res, t); continue;}
            if(t > d[x1][y1][x2][y2]){continue;}

            REP(i, 4){
                int nx1 = x1 + dx[i], ny1 = y1 + dy[i],
                    nx2 = x2 - dx[i], ny2 = y2 - dy[i];

                if(X <= nx1 || nx1 < 0 || Y <= ny1 || ny1 < 0 ||
                   map[ny1][nx1] == 1){
                    nx1 = x1; ny1 = y1;
                }

                if(X <= nx2 || nx2 < 0 || Y <= ny2 || ny2 < 0 ||
                   map[ny2][nx2] == 1){
                    nx2 = x2; ny2 = y2;
                }

                if(t + 1 < d[nx1][ny1][nx2][ny2]){
                    d[nx1][ny1][nx2][ny2] = t + 1;
                    q.push(mp(d[nx1][ny1][nx2][ny2], mp(mp(nx1, ny1), mp(nx2, ny2))));
                }
            }
        }

        if(res == INF){
            puts("NA");
        }else{
            printf("%d\n", res);
        }
    }
}