Go: package main

import (
	"container/heap"
	"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)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		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)
			}
		}
	}
	fmt.Println("NA")
}

func main() {
	var h, w int64
	for {
		fmt.Scan(&h, &w)
		if h == 0 && w == 0 {
			break
		}
		solve(h, w)
	}
}

Python: from collections import deque
dd = ((-1, 0), (0, -1), (1, 0), (0, 1))

DD = [-1, 1]
while 1:
    W, H = map(int, input().split())
    if W == H == 0:
        break
    tx, ty = map(int, input().split())
    kx, ky = map(int, input().split())
    D = [list(map(int, input().split())) for i in range(H)]
    que = deque()
    push = que.append
    pop = que.popleft
    key = (tx-1, ty-1, kx-1, ky-1)
    push(key)
    dist = {key: 0, (kx-1, ky-1, tx-1, ty-1): 0}
    while que:
        x0, y0, x1, y1 = key = pop()
        d = dist[key]
        if x0 == x1 and y0 == y1:
            print(d)
            break
        if d == 99:
            continue
        for dx in DD:
            nx0 = x0 + dx
            if not 0 <= nx0 < W or D[y0][nx0]:
                nx0 = x0
            nx1 = x1 - dx
            if not 0 <= nx1 < W or D[y1][nx1]:
                nx1 = x1
            key = (nx0, y0, nx1, y1)
            if key not in dist:
                dist[key] = d + 1
                push(key)
                key = (nx1, y1, nx0, y0)
                dist[key] = d + 1
        for dy in DD:
            ny0 = y0 + dy
            if not 0 <= ny0 < H or D[ny0][x0]:
                ny0 = y0
            ny1 = y1 - dy
            if not 0 <= ny1 < H or D[ny1][x1]:
                ny1 = y1
            key = (x0, ny0, x1, ny1)
            if key not in dist:
                dist[key] = d + 1
                push(key)
                key = (x1, ny1, x0, ny0)
                dist[key] = d + 1
    else:
        print("NA")

Python: from collections import deque

while(True):
    W, H = map(int, input().split())
    if not W: break
    tx,ty = map(int, input().split())
    kx,ky = map(int, input().split())
    ma = [[False]*(W+2) for _ in range(H+2)]
    for i in range(1,H+1):
        for j,a in enumerate(input().split()):
            ma[i][j+1] = bool(1-int(a))
    from pprint import pprint
    que = deque([[tx,ty,kx,ky,0]])
    pas = set()
    ans = "NA"
    while(que):
        tx,ty,kx,ky,c = que.popleft()
        if c > 100: break
        if tx == kx and ty == ky:
            ans = c
            break
        for dx,dy in [[-1,0],[0,-1],[1,0],[0,1]]:
            tdx, tdy = [ dx, dy] if ma[ty+dy][tx+dx] else [0,0]
            kdx, kdy = [-dx,-dy] if ma[ky-dy][kx-dx] else [0,0]
            if (tx+tdx,ty+tdy,kx+kdx,ky+kdy) in pas: continue
            que.append([tx+tdx,ty+tdy,kx+kdx,ky+kdy,c+1])
            pas.add((tx+tdx,ty+tdy,kx+kdx,ky+kdy))
    print(ans)

Python: from collections import deque

def search(tx, ty, kx, ky, mp):
  direct = ((-1, 0, 1, 0), (1, 0, -1, 0), (0, -1, 0, 1), (0, 1, 0, -1))
  dic = {}
  dic[(tx, ty, kx, ky)] = 0
  que = deque()
  que.append((0, (tx, ty, kx, ky)))
  while que:
    dist, p = que.popleft()
    tx, ty, kx, ky = p
    for dtx, dty, dkx, dky in direct:
      if mp[ty + dty][tx + dtx] == 0:
        ntx, nty = tx + dtx, ty + dty
      else:
        ntx, nty = tx, ty
      if mp[ky + dky][kx + dkx] == 0:
        nkx, nky = kx + dkx, ky + dky
      else:
        nkx, nky = kx, ky
      if (ntx, nty, nkx, nky) not in dic:
        if (ntx, nty) == (nkx, nky):
          print(dist + 1)
          return
        dic[(ntx, nty, nkx, nky)] = True
        que.append((dist + 1, (ntx, nty, nkx, nky)))
  else:
    print("NA")

while True:
  w, h = map(int, input().split())
  if w == 0:
    break
  tx, ty = map(int, input().split())
  kx, ky = map(int, input().split())
  mp = [[1] + list(map(int, input().split())) + [1] for _ in range(h)]
  mp.insert(0, [1] * (w + 2))
  mp.append([1] * (w + 2))

  search(tx, ty, kx, ky, mp)

Python: direc = ((1,0),(-1,0),(0,1),(0,-1))


#d = [[[[0 for i in range(Y+1)] for i in range(X+1)] for i in range(Y+1)] for i in range(X+1)]
#d[1][1][2][2]=3
# print(d)
while 1:
    X, Y = list(map(int,input().split()))
    if X == 0: break

    ftx, fty = list(map(lambda x: x-1, map(int, input().split())))
    fkx, fky = list(map(lambda x: x-1, map(int, input().split())))

    m = [list(map(int, input().split())) for i in range(Y)]

    d = {(ftx, fty, fkx, fky): 0}

    s = [[0, (ftx, fty, fkx, fky)]]
    res = 'NA'
    while len(s) > 0:
        spm = s.pop(0)
        cnt = spm[0] + 1
        if cnt > 100:
            break

        def search_move():
            for i in range(4):
                tx = spm[1][0]+direc[i][0]
                ty = spm[1][1]+direc[i][1]
                kx = spm[1][2]-direc[i][0]
                ky = spm[1][3]-direc[i][1]


                hm = 0
                if tx < 0 or tx >= X or ty < 0 or ty >= Y or m[ty][tx] == 1:
                    tx = ftx
                    ty = fty
                    hm += 1
                if kx < 0 or kx >= X or ky < 0 or ky >= Y or m[ky][kx] == 1:
                    kx = fkx
                    ky = fky
                    hm += 1

                if hm == 2: continue
                tpl = (tx,ty,kx,ky)
                if tpl in d and d[tpl] <= cnt:
                    continue

                if tx == kx and ty == ky:
                    return True
                else:
                    s.append([cnt,tpl])
                    d[tpl] = cnt
    #            print(tpl)
            return False
        if search_move():
            res = str(cnt)
            break
    print(res)