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)
	}
}

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)

Python: # from line_profiler import LineProfiler
from collections import deque

def main():
    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)

if __name__ == "__main__":
    # prf = LineProfiler()
    # prf.add_function(main)
    # prf.runcall(main)
    # prf.print_stats()
    main()

Python: # from line_profiler import LineProfiler
from collections import deque
from sys import stdin

def main():
    while(True):
        W, H = map(int, stdin.readline().split())
        if not W: break
        tx,ty = map(int, stdin.readline().split())
        kx,ky = map(int, stdin.readline().split())
        ma = [[0]+[abs(1-int(a)) for a in stdin.readline().split()]+[0] for i in range(H)]
        ma = [[0]*(W+2)] + ma + [[0]*(W+2)]
        que = deque([[tx,ty,kx,ky,0]])
        pas = set()
        ans = "NA"
        while(que):
            tx,ty,kx,ky,c = que.popleft()
            if tx == kx and ty == ky:
                ans = c
                break
            if c+1 > 100: continue
            for dx,dy in [[-1,0],[0,-1],[1,0],[0,1]]:
                tdx, tdy =  dx * ma[ty+dy][tx+dx],  dy * ma[ty+dy][tx+dx]
                kdx, kdy = -dx * ma[ky-dy][kx-dx], -dy * ma[ky-dy][kx-dx]
                ttx,tty,kkx,kky = tx+tdx,ty+tdy,kx+kdx,ky+kdy
                if (ttx,tty,kkx,kky) in pas: continue
                que.append([ttx,tty,kkx,kky,c+1])
                pas.add((ttx,tty,kkx,kky))
        print(ans)

if __name__ == "__main__":
    # prf = LineProfiler()
    # prf.add_function(main)
    # prf.runcall(main)
    # prf.print_stats()
    main()