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 <iostream>
#include <queue>
#include <algorithm>
#include <cstring>
using namespace std;

#define MAX_Y 50
#define MAX_X 50

int X, Y;
bool F[MAX_Y][MAX_X];

struct S {
    int ty, tx, ky, kx;
    int t;
    S(int ty, int tx, int ky, int kx, int t) : ty(ty), tx(tx), ky(ky), kx(kx), t(t){} 
};

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

bool used[MAX_Y][MAX_X][MAX_Y][MAX_X];
int bfs(int ty, int tx, int ky, int kx) {
    memset(used, 0, sizeof(used));
    queue<S> q;
    q.push(S(ty, tx, ky, kx, 0));
    while (!q.empty()) {
        S s = q.front(); q.pop();
        if (s.ty == s.ky && s.tx == s.kx) return s.t;
        if (s.t >= 100) break;
        for (int i = 0; i < 4; i++) {
            int nty = s.ty + dty[i],
                ntx = s.tx + dtx[i],
                nky = s.ky + dky[i],
                nkx = s.kx + dkx[i],
                nt  = s.t + 1;
            if (0 <= nty && nty < Y && 0 <= ntx && ntx < X) {
                if (F[nty][ntx]) {
                    nty = s.ty, ntx = s.tx;
                }
            } else {
                nty = s.ty, ntx = s.tx;
            }
            if (0 <= nky && nky < Y && 0 <= nkx && nkx < X) {
                if (F[nky][nkx]) {
                    nky = s.ky, nkx = s.kx;
                }
            } else {
                nky = s.ky, nkx = s.kx;
            }
            if (used[nty][ntx][nky][nkx]) continue;
            q.push(S(nty, ntx, nky, nkx, nt));
            used[nty][ntx][nky][nkx] = true;
        }
    }
    return -1;
}

int main() {
    while (cin >> X >> Y, X || Y) {
        int tx, ty, kx, ky;
        cin >> tx >> ty >> kx >> ky;
        ty--, tx--, ky--, kx--;
        for (int i = 0; i < Y; i++) {
            for (int j = 0; j < X; j++) {
                cin >> F[i][j];
            }
        }
        int t = bfs(ty, tx, ky, kx);
        if (t >= 0) {
            cout << t << endl;
        } else {
            cout << "NA" << endl;
        }
    }
    return 0;
}