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)
	}
}

C++: #include<iostream>
#include<queue>
#include<map>
using namespace std;
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
class state {
public:
	int tx;
	int ty;
	int kx;
	int ky;
	int time;
	bool operator < (const state &s)const {
		if (ty != s.ty)return ty < s.ty;
		if (tx != s.tx)return tx < s.tx;
		if (ky != s.ky)return ky < s.ky;
		if (kx != s.kx)return kx < s.kx;
		return false;
	}
};
int main() {
	int W, H, tx, ty, kx, ky;
	bool d[52][52];
	state num;
	state copy;
	while (true) {
		map<state, bool> m;
		queue<state> q;
		cin >> W >> H;
		if (W == 0)break;
		for (int i = 0; i < H + 2; i++) {
			for (int j = 0; j < W + 2; j++) {
				d[i][j] = 1;
			}
		}
		cin >> tx >> ty >> kx >> ky;
		for (int i = 1; i < H + 1; i++) {
			for (int j = 1; j < W + 1; j++) {
				cin >> d[j][i];
			}
		}
		num.tx = tx;
		num.ty = ty;
		num.kx = kx;
		num.ky = ky;
		num.time = 0;
		q.push(num);
		while (!q.empty()) {
			num = q.front();
			q.pop();
			if (num.time == 100) {
				cout << "NA" << endl;
				break;
			}
			if (num.tx == num.kx && num.ty == num.ky) {
				cout << num.time << endl;
				break;
			}
			for (int i = 0; i < 4; i++) {
				copy = num;
				copy.time++;
				if (!d[num.tx + dx[i]][num.ty + dy[i]]) {
					copy.tx = num.tx + dx[i];
					copy.ty = num.ty + dy[i];
				}
				if (!d[num.kx - dx[i]][num.ky - dy[i]]) {
					copy.kx = num.kx - dx[i];
					copy.ky = num.ky - dy[i];
				}
				if (!m[copy]) {
					m[copy] = true;
					q.push(copy);
				}
			}
			if (q.empty()) {
				cout << "NA" << endl;
			}
		}
	}
	return 0;
}

C++: #include <cstdio>
#include <queue>
#include <utility>
#include <set>
using namespace std;
typedef pair<int,int> P_;
typedef pair<P_,P_> _P;
typedef pair<_P,int> P;
int M[50][50];
int dx1[]={1,0,-1,0},dy1[]={0,1,0,-1};
int dx2[]={-1,0,1,0},dy2[]={0,-1,0,1};
int main() {
	int X,Y;
	while(scanf("%d %d",&X,&Y),X) {
		int tx,ty,kx,ky;
		scanf("%d %d %d %d",&tx,&ty,&kx,&ky);
		tx--;ty--;kx--;ky--;
		for(int y=0;y<Y;y++) {
			for(int x=0;x<X;x++) {
				scanf("%d",&M[x][y]);
			}
		}
		set<_P> ST;
		ST.insert(_P(P_(tx,ty),P_(kx,ky)));
		queue<P> Q;
		Q.push(P(_P(P_(tx,ty),P_(kx,ky)),0));
		bool OK=false;
		while(!Q.empty()) {
			P p=Q.front();Q.pop();
			P_ T=p.first.first,K=p.first.second;
			if(p.second>=100)break;
			if(T.first==K.first&&T.second==K.second) {
					printf("%d\n",p.second);
					OK=true;
					break;
			}
			for(int i=0;i<4;i++) {
				int ntx=T.first+dx1[i],nty=T.second+dy1[i];
				int nkx=K.first+dx2[i],nky=K.second+dy2[i];
				if(0>ntx||ntx>=X||0>nty||nty>=Y||M[ntx][nty])
					ntx=T.first,nty=T.second;
				if(0>nkx||nkx>=X||0>nky||nky>=Y||M[nkx][nky])
					nkx=K.first,nky=K.second;
				if(ST.find(_P(P_(ntx,nty),P_(nkx,nky)))==ST.end()) {
					ST.insert(_P(P_(ntx,nty),P_(nkx,nky)));
					Q.push(P(_P(P_(ntx,nty),P_(nkx,nky)),p.second+1));
				}
			}
		}
		if(!OK)printf("NA\n");
	}
}

C++: #include <iostream>
#include <cstring>
#include <queue>
using namespace std;

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

struct State { int tx, ty, kx, ky, cost; };
int X, Y;
int d[52][52];
bool used[52][52][52][52];

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	while (cin >> X >> Y, X) {
		int tx, ty, kx, ky;
		cin >> tx >> ty >> kx >> ky;
		for (int i=0; i<=Y+1; ++i) {
			for (int j=0; j<=X+1; ++j) {
				if (i==0 || i==Y+1 || j==0 || j==X+1) d[i][j] = 1;
				else cin >> d[i][j];
			}
		}
		memset(used, false, sizeof used);
		queue<State> q;
		q.push((State){tx, ty, kx, ky, 0});
		int res = -1;
		while ( ! q.empty()) {
			State s = q.front(); q.pop();
			if (100 <= s.cost) break;
			if (used[s.tx][s.ty][s.kx][s.ky]) continue;
			used[s.tx][s.ty][s.kx][s.ky] = true;
			if (s.tx == s.kx && s.ty == s.ky) {
				res = s.cost;
				break;
			}
			for (int i=0; i<4; ++i) {
				if (d[s.ty+dy[i]][s.tx+dx[i]] && d[s.ky-dy[i]][s.kx-dx[i]]) continue;
				int tx2 = s.tx, ty2 = s.ty;
				if ( ! d[s.ty+dy[i]][s.tx+dx[i]]) {
					tx2 += dx[i];
					ty2 += dy[i];
				}
				int kx2 = s.kx, ky2 = s.ky;
				if ( ! d[s.ky-dy[i]][s.kx-dx[i]]) {
					kx2 -= dx[i];
					ky2 -= dy[i];
				}
				if ( ! used[tx2][ty2][kx2][ky2] && s.cost+1 < 100) {
					q.push((State){tx2, ty2, kx2, ky2, s.cost+1});
				}
			}
		}
		if (res < 0) {
			cout << "NA" << endl;
		} else {
			cout << res << endl;
		}
	}
	return 0;
}