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 := 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)
	}
}

C++: #define _USE_MATH_DEFINES
#define INF 10000000
#include <iostream>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <limits>
#include <map>
#include <string>
#include <cstring>
#include <set>
#include <deque>
#include <bitset>
#include <list>

using namespace std;

typedef long long ll;
typedef pair <int,int> P;
typedef pair <P,P> PP;
typedef pair <int,PP> PPP;

static const double eps = 1e-8;

static const int moveTo[][2] = {{1,0},{0,-1},{-1,0},{0,1}};
static const int moveToRev[][2] = {{-1,0},{0,1},{1,0},{0,-1}};

int stage[50][50];
int costTable[50][50][50][50];

int bfs(int tx,int ty,int kx,int ky,int w,int h){
	priority_queue<PPP,vector<PPP>,greater<PPP> > que;
	que.push(PPP(0,PP(P(tx,ty),P(kx,ky))));	
	memset(costTable,0x3,sizeof(costTable));

	int res = INF;
	costTable[tx][ty][kx][ky] = 0;
	while(!que.empty()){
		int cost = que.top().first;
		if(res <= cost || cost > 100){
			que.pop(); continue;
		}

		int tx = que.top().second.first.first;
		int ty = que.top().second.first.second;
		int kx = que.top().second.second.first;
		int ky = que.top().second.second.second;

		if(tx==kx && ty == ky) res = min(res,cost);

		que.pop();

		for(int i=0;i<4;i++){
			int tdx = tx + moveTo[i][0];
			int tdy = ty + moveTo[i][1];

			if((tdx < 0 || tdx >= w || tdy < 0 || tdy >=h) || stage[tdy][tdx]) {
				tdx = tx;
				tdy = ty;
			}

			int kdx = kx + moveToRev[i][0];
			int kdy = ky + moveToRev[i][1];

			if((kdx < 0 || kdx >= w || kdy < 0 || kdy >=h) || stage[kdy][kdx]) {
				kdx = kx;
				kdy = ky;
			}
			if(costTable[tdx][tdy][kdx][kdy] <= cost + 1) continue;
			costTable[tdx][tdy][kdx][kdy] = cost + 1;
			que.push(PPP(cost+1,PP(P(tdx,tdy),P(kdx,kdy))));
		}
	}

	return res;
}

int main(){

	int w,h;
	while(~scanf("%d %d",&w,&h)){
		if(w ==h && h==0) break;
		int tx,ty;
		scanf("%d %d",&tx,&ty);
		int kx,ky;
		scanf("%d %d",&kx,&ky);
		for(int y=0;y<h;y++){
			for(int x=0;x<w;x++){
				scanf("%d",&stage[y][x]);
			}
		}

		int res = bfs(tx,ty,kx,ky,w,h);
		if(res >= 100) printf("NA\n");
		else printf("%d\n",res);
	}
}

C++: #include <iostream>
#include <algorithm>
#include <queue>
#include <utility>
#include <map>
using namespace std;

const int Y = 50, X = 50, GUARD = 1;
typedef pair<int, int> P;


int bfs(const int (*board)[Y + 2], P t, P k){
	int dx[] = {0, -1, 1, 0}, dy[] = {-1, 0, 0, 1};
	// pair<P, P> -> first = t, second = k
	queue<pair<P, P> > q;
	map<pair<P, P>, int> visited;
	q.push(make_pair(t, k));
	visited[make_pair(t, k)] = 0;
	while(!q.empty()){
		pair<P, P> picked = q.front();
		q.pop();
		if(visited[picked] >= 100) return -1;
		P ct = picked.first, ck = picked.second;
		if(ct == ck) return visited[picked];
		for(int i = 0;i < 4;++i){
			pair<P, P> nextp;
			P nextt, nextk;
			int tdx, tdy, kdx, kdy;
			int ntx, nty, nkx, nky;
			tdx = dx[i];
			tdy = dy[i];
			kdx = -tdx;
			kdy = -tdy;

			ntx = ct.first + tdx;
			nty = ct.second + tdy;
			nkx = ck.first + kdx;
			nky = ck.second + kdy;

			nextt = board[ntx][nty] != GUARD ? P(ntx, nty) : ct;
			nextk = board[nkx][nky] != GUARD ? P(nkx, nky) : ck;
			nextp = make_pair(nextt, nextk);

			if(visited[nextp] == 0){
				q.push(nextp);
				visited[nextp] = visited[picked] + 1;
			}
		}
	}
	return -1;
}

int main(){
	int board[X + 2][Y + 2];
	int x, y, a, res;
	P t, k;
	while(cin >> x >> y, x && y){
		for(int i = 0;i <= X + 1;++i){
			fill(board[i], board[i] + (Y + 2), GUARD);
		}
		cin >> t.first >> t.second;
		cin >> k.first >> k.second;
		for(int i = 1;i <= y;++i){
			for(int j = 1;j <= x;++j){
				cin >> a;
				board[i][j] = a;
			}
		}
		res = bfs(board, t, k);
		if(res != -1) cout << res << endl;
		else cout << "NA" << endl;
	}
	return 0;
}