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 <cstdio>
#include <cstdlib>
#include <string>
#include <vector>
#include <deque>
#include <list>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <cstring>
#include <cctype>
#include <sstream>
#include <set>
#include <map>
#include <queue>
#include <complex>
using namespace std;

int main() {
	int X, Y;
	while(cin >> X >> Y, X|Y) {
		bool b = true;
		int tx, ty, kx, ky, map[Y][X];
		cin >> tx >> ty >> kx >> ky;
		for(int i=0; i<Y; i++)
			for(int j=0; j<X; j++)
				cin >> map[i][j];

		queue<int> q;
		set<int> memo;

		q.push(0);
		q.push((tx-1)*1000000+(ty-1)*10000+(kx-1)*100+ky-1);

		while(q.size()) {
			int tx2, ty2, kx2, ky2, chk, cnt;
			cnt = q.front();
			q.pop();
			tx = q.front() /1000000;
			ty = q.front() /10000 %100;
			kx = q.front() /100 %100;
			ky = q.front() %100;
//			cout << q.front() << endl;

			if(tx == kx && ty == ky) {
				b = false;
				cout << cnt << endl;
				break;
			}
			if(cnt==100) {
				b = false;
				cout << "NA" << endl;
				break;
			}
			if(ty>0 && !map[ty-1][tx]) {
				ty--;
				if(ky<Y-1 && !map[ky+1][kx])
					ky++;
				chk = tx*1000000+ty*10000+kx*100+ky;
				if(memo.find(chk) == memo.end()) {
					memo.insert(chk);
					q.push(cnt+1);
					q.push(chk);
				}
				ty = q.front() /10000 %100;
				ky = q.front() %100;
			}
			if(tx>0 && !map[ty][tx-1]) {
				tx--;
				if(kx<X-1 && !map[ky][kx+1])
					kx++;
				chk = tx*1000000+ty*10000+kx*100+ky;
				if(memo.find(chk) == memo.end()) {
					memo.insert(chk);
					q.push(cnt+1);
					q.push(chk);
				}
				tx = q.front() /1000000;
				kx = q.front() /100 %100;
			}
			if(ty<Y-1 && !map[ty+1][tx]) {
				ty++;
				if(ky>0 && !map[ky-1][kx])
					ky--;
				chk = tx*1000000+ty*10000+kx*100+ky;
				if(memo.find(chk) == memo.end()) {
					memo.insert(chk);
					q.push(cnt+1);
					q.push(chk);
				}
				ty = q.front() /10000 %100;
				ky = q.front() %100;
			}
			if(tx<X-1 && !map[ty][tx+1]) {
				tx++;
				if(kx>0 && !map[ky][kx-1])
					kx--;
				chk = tx*1000000+ty*10000+kx*100+ky;
				if(memo.find(chk) == memo.end()) {
					memo.insert(chk);
					q.push(cnt+1);
					q.push(chk);
				}
				tx = q.front() /1000000;
				kx = q.front() /100 %100;
			}

			if(ky>0 && !map[ky-1][kx]) {
				ky--;
				if(ty<Y-1 && !map[ty+1][tx])
					ty++;
				chk = tx*1000000+ty*10000+kx*100+ky;
				if(memo.find(chk) == memo.end()) {
					memo.insert(chk);
					q.push(cnt+1);
					q.push(chk);
				}
				ty = q.front() /10000 %100;
				ky = q.front() %100;
			}
			if(kx>0 && !map[ky][kx-1]) {
				kx--;
				if(tx<X-1 && !map[ty][tx+1])
					tx++;
				chk = tx*1000000+ty*10000+kx*100+ky;
				if(memo.find(chk) == memo.end()) {
					memo.insert(chk);
					q.push(cnt+1);
					q.push(chk);
				}
				tx = q.front() /1000000;
				kx = q.front() /100 %100;
			}
			if(ky<Y-1 && !map[ky+1][kx]) {
				ky++;
				if(ty>0 && !map[ty-1][tx])
					ty--;
				chk = tx*1000000+ty*10000+kx*100+ky;
				if(memo.find(chk) == memo.end()) {
					memo.insert(chk);
					q.push(cnt+1);
					q.push(chk);
				}
				ty = q.front() /10000 %100;
				ky = q.front() %100;
			}
			if(kx<X-1 && !map[ky][kx+1]) {
				kx++;
				if(tx>0 && !map[ty][tx-1])
					tx--;
				chk = tx*1000000+ty*10000+kx*100+ky;
				if(memo.find(chk) == memo.end()) {
					memo.insert(chk);
					q.push(cnt+1);
					q.push(chk);
				}
				tx = q.front() /1000000;
				kx = q.front() /100 %100;
			}
			q.pop();
		}
		if(b) cout << "NA" << endl;
	}
	return 0;
}