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)
	pq = append(pq, 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)
		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 += 1
			if next.Turn <= 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				pq = append(pq, 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 <utility>
#include <set>
#include <vector>
using namespace std;

int main(void) {
	int X, Y;

	while(cin >> X >> Y, X | Y) {
		pair<int,int> t, k;
		vector<vector<int> > depart;
		set<pair<pair<int,int>,pair<int,int> > > moved;
		queue<pair<pair<pair<int,int>, pair<int,int> >, int> > q;
		int ans = -1;

		cin >> t.second >> t.first; t.first--; t.second--;
		cin >> k.second >> k.first; k.first--; k.second--;

		for(int i = 0; i < Y; i++) {
			vector<int> v;
			for(int j = 0; j < X; j++) {
				int tmp;
				cin >> tmp;
				v.push_back(tmp);
			}
			depart.push_back(v);
		}

		moved.insert(make_pair(t, k));
		q.push(make_pair(make_pair(t,k), 0));

		for(int i = 0;; i++) {
			pair<pair<int,int>, pair<int, int> > p;
			pair<int, int> next_t, next_k;
			int n;

			if(q.empty()) {
				break;
			}

			p = q.front().first; n = q.front().second; q.pop();
			if(p.first == p.second) {
				ans = n;
				break;
			}
			if(n > 100)
				break;

			next_t.first = p.first.first; next_t.second = p.first.second;
			next_k.first = p.second.first; next_k.second = p.second.second;
			if(p.first.first + 1 < Y && depart[p.first.first + 1][p.first.second] == 0) {
				next_t.first = p.first.first + 1;
				next_t.second = p.first.second;
			}
			if(p.second.first - 1 >= 0 && depart[p.second.first - 1][p.second.second] == 0) {
				next_k.first = p.second.first - 1;
				next_k.second = p.second.second;
			}
			if(moved.insert(make_pair(next_t, next_k)).second) {
				q.push(make_pair(make_pair(next_t, next_k),n + 1));
			}

			next_t.first = p.first.first; next_t.second = p.first.second;
			next_k.first = p.second.first; next_k.second = p.second.second;
			if(p.first.first - 1 >= 0 && depart[p.first.first - 1][p.first.second] == 0) {
				next_t.first = p.first.first - 1;
				next_t.second = p.first.second;
			}
			if(p.second.first + 1 < Y && depart[p.second.first + 1][p.second.second] == 0) {
				next_k.first = p.second.first + 1;
				next_k.second = p.second.second;
			}
			if(moved.insert(make_pair(next_t, next_k)).second) {
				q.push(make_pair(make_pair(next_t, next_k),n + 1));
			}

			next_t.first = p.first.first; next_t.second = p.first.second;
			next_k.first = p.second.first; next_k.second = p.second.second;
			if(p.first.second + 1 < X && depart[p.first.first][p.first.second + 1] == 0) {
				next_t.first = p.first.first;
				next_t.second  = p.first.second + 1;
			}
			if(p.second.second - 1 >= 0 && depart[p.second.first][p.second.second - 1] == 0) {
				next_k.first = p.second.first;
				next_k.second  = p.second.second - 1;
			}
			if(moved.insert(make_pair(next_t, next_k)).second) {
				q.push(make_pair(make_pair(next_t, next_k),n + 1));
			}

			next_t.first = p.first.first; next_t.second = p.first.second;
			next_k.first = p.second.first; next_k.second = p.second.second;
			if(p.first.second - 1 >= 0 && depart[p.first.first][p.first.second - 1] == 0) {
				next_t.first = p.first.first;
				next_t.second  = p.first.second - 1;
			}
			if(p.second.second + 1 < X && depart[p.second.first][p.second.second + 1] == 0) {
				next_k.first = p.second.first;
				next_k.second  = p.second.second + 1;
			}
			if(moved.insert(make_pair(next_t, next_k)).second) {
				q.push(make_pair(make_pair(next_t, next_k),n + 1));
			}
		}

		if(ans != -1)
			cout << ans << endl;
		else
			cout << "NA" << endl;
	}
}