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 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 = [[False]*(W+2) for _ in range(H+2)]
        for i in range(1,H+1):
            for j,a in enumerate(stdin.readline().split()):
                ma[i][j+1] = bool(1-int(a))
        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
            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
                if c+1 > 100: 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 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):
          if dist + 1 >= 100:
            print("NA")
          else:
            print(dist + 1)
          return
        dic[(ntx, nty, nkx, nky)] = True
        que.append((dist + 1, (ntx, nty, nkx, nky)))
  else:
    print("NA")

def main():
  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)

main()

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))
        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()

C++: #include<iostream>
#include<string>
#include<map>
#include<queue>

#define rep(i,n) for(int i=0;i<int(n);i++)
#define sint(i) scanf("%d",&i);
#define sintt(i,j) scanf("%d%d",&i,&j);
using namespace std;

int xx,yy;

class Q{
	public:
	int bx,by,bbx,bby;
	int dep;
	Q(int bx,int by,int bbx,int bby,int dep):
	bx(bx),by(by),bbx(bbx),bby(bby),dep(dep){}
};

int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};

int masu[51][51];
int memo[51][51][51][51];

int search(int bx,int by,int bbx,int bby){
	
	queue<Q> hako;
	
	hako.push(Q(bx,by,bbx,bby,0));
	
	while(1){
		if(hako.empty()==1){
			break;
		}
		
		Q u=hako.front();
		hako.pop();
		
		if(u.dep>=100){
			break;
		}
		if(u.bx<=0 || u.by<=0 || u.bx>xx || u.by>yy || masu[u.bx][u.by]==1){
			continue;
		}
		if(u.bbx<=0 || u.bby<=0 || u.bbx>xx || u.bby>yy || masu[u.bbx][u.bby]==1){
			continue;
		}
		
		if(memo[u.bx][u.by][u.bbx][u.bby]==1){
			continue;
		}else{
			memo[u.bx][u.by][u.bbx][u.bby]=1;
		}
		if(u.bx==u.bbx && u.by==u.bby){
			return u.dep;
		}
		
		
		rep(i,4){
			hako.push(Q(u.bx+dx[i],u.by+dy[i],u.bbx+dx[(i+2)%4],u.bby+dy[(i+2)%4],u.dep+1));
		}
	}
	return -1;
}

int main(){
	while(1){
		sintt(xx,yy);
		
		if(xx==0){
			break;
		}
		int bx,by,bbx,bby;
		sintt(bx,by);
		sintt(bbx,bby);
		
		rep(i,51)rep(j,51)rep(k,51)rep(p,51){
		memo[i][j][k][p]=0;
		}
		
		rep(i,yy){
			rep(j,xx){
				sint(masu[j+1][i+1]);
			}
		}
		
		int ans=search(bx,by,bbx,bby);
		if(ans==-1){
			puts("NA");
		}else{
			printf("%d\n",ans);
		}
	}
}