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 ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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 <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstring>
#include <sstream>
using namespace std;
static const double EPS = 1e-5;
typedef long long ll;
#define rep(i,n) for(int i=0;i<n;i++)


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

main(){
	int x,y;
	while(cin>>x>>y,x){
		int tx,ty,kx,ky;
		cin>>tx>>ty>>kx>>ky;
		int d[x][y];
		--tx;
		--ty;
		--kx;
		--ky;
		rep(i,x)rep(j,y)cin>>d[i][j];
		
		queue<pair<pair<pair<int,int>,pair<int,int> >,int> > state;
		set<pair<pair<int,int>,pair<int,int> > > past;
		
		state.push(make_pair(make_pair(make_pair(tx,ty),make_pair(kx,ky)),0));
		
		past.insert(make_pair(make_pair(tx,ty),make_pair(kx,ky)));
		
		int time=0;
		bool na=true;
		
		while(!state.empty()){
			pair<pair<int,int>,pair<int,int> > tp=state.front().first;
			time=state.front().second;
			state.pop();
			if(time>=100)break;
			if(tp.first==tp.second){
				na=false;
				break;
			}
			
			rep(i,4){
				int ttx=tp.first.first+dx[i],tty=tp.first.second+dy[i],
					tkx=tp.second.first-dx[i],tky=tp.second.second-dy[i];
				
				if(ttx<0 || ttx>=x || tty<0 || tty>=y || d[ttx][tty]==1){
					ttx-=dx[i];
					tty-=dy[i];
				}
				if(tkx<0 || tkx>=x || tky<0 || tky>=y || d[tkx][tky]==1){
					tkx+=dx[i];
					tky+=dy[i];
				}
				pair<pair<int,int>,pair<int,int> > next=make_pair(make_pair(ttx,tty),make_pair(tkx,tky));
				
				if(past.count(next))continue;
				past.insert(next);
				state.push(make_pair(next,time+1));
			}
		}
		
		if(na)puts("NA");
		else cout<<time<<endl;
	}
}

C++: //1.includes
#include<iostream>
#include<queue>
#include<tuple>
#include<algorithm>
using namespace std;
//2.defines
#define MAX_N 60
#define INF 1000000000
//3.variables
int dp[MAX_N][MAX_N][MAX_N][MAX_N];
int H, W, A1, A2, B1, B2;
int x[MAX_N][MAX_N];
queue<tuple<int, int, int, int>>Q;
//4.functions
int solve() {
	dp[A1][A2][B1][B2] = 0;
	Q.push(make_tuple(A1, A2, B1, B2));
	while (!Q.empty()) {
		tuple<int, int, int, int>tup = Q.front();
		Q.pop();
		int a1 = get<0>(tup);
		int a2 = get<1>(tup);
		int a3 = get<2>(tup);
		int a4 = get<3>(tup);
		int dx[4] = { 1,0,-1,0 };
		int dy[4] = { 0,-1,0,1 };
		for (int i = 0; i < 4; i++) {
			int cx = a1 + dx[i], cy = a2 + dy[i];
			int ex = a3 - dx[i], ey = a4 - dy[i];
			if (x[cx][cy] == 1) { cx = a1; cy = a2; }
			if (x[ex][ey] == 1) { ex = a3; ey = a4; }
			if (dp[cx][cy][ex][ey] > dp[a1][a2][a3][a4] + 1) {
				dp[cx][cy][ex][ey] = dp[a1][a2][a3][a4] + 1;
				Q.push(make_tuple(cx, cy, ex, ey));
			}
		}
	}
	int minx = INF;
	for (int i = 1; i <= H; i++) {
		for (int j = 1; j <= W; j++) {
			minx = min(minx, dp[i][j][i][j]);
		}
	}
	return minx;
}
void _memset() {
	for (int i = 0; i < MAX_N; i++) {
		for (int j = 0; j < MAX_N; j++) {
			for (int k = 0; k < MAX_N; k++) {
				for (int l = 0; l < MAX_N; l++) {
					dp[i][j][k][l] = INF;
				}
			}
		}
	}
	for (int i = 0; i < MAX_N; i++) {
		for (int j = 0; j < MAX_N; j++) {
			x[i][j] = 1;
		}
	}
}
int main() {
	while (true) {
		_memset();
		cin >> H >> W;
		if (H == 0 && W == 0) { break; }
		cin >> A1 >> A2 >> B1 >> B2;
		for (int i = 1; i <= H; i++) {
			for (int j = 1; j <= W; j++) {
				cin >> x[j][i];
			}
		}
		int v = solve();
		if (v >= 100) { cout << "NA" << endl; }
		else { cout << v << endl; }
	}
	return 0;
}

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

using namespace std;


struct P {
	int x, y;
};

struct data {
	P tp, kp;
	int step;
};

bool used[50][50][50][50] = {0};
int m[50][50];
int W, H;

P move(P p, P d) {
	P next = (P){ p.x+d.x, p.y+d.y };
	if (next.x < 0 || next.x >= W || next.y < 0 || next.y >= H) return p;
	if (m[next.y][next.x]) return p;
	return next;
}

int main() {
	while ( cin >> W >> H, W || H ) {
		int tx, ty; cin >> tx >> ty; --tx, --ty;
		int kx, ky; cin >> kx >> ky; --kx, --ky;
		for (int y = 0; y < H; ++y) {
			for (int x = 0; x < W; ++x) {
				cin >> m[y][x];
			}
		}
		fill(&used[0][0][0][0], &used[0][0][0][0]+50*50*50*50, false);
		queue<data> Q; Q.push( (data){ (P){tx, ty}, (P){kx, ky}, 0} );
		int ans = -1;
		while ( !Q.empty() ) {
			data d = Q.front(); Q.pop();
			P tp = d.tp, kp = d.kp;

			if (tp.x < 0 || tp.x >= W || tp.y < 0 || tp.y >= H) continue;
			if (kp.x < 0 || kp.x >= W || kp.y < 0 || kp.y >= H) continue;
			if (m[tp.y][tp.x]) continue;
			if (m[kp.y][kp.x]) continue;

			if (used[tp.x][tp.y][kp.x][kp.y]) continue;
			used[tp.x][tp.y][kp.x][kp.y] = true;

			if (tp.x == kp.x && tp.y == kp.y) {
				ans = d.step;
				break;
			}

			Q.push( (data){ move(tp, (P){0, 1}), move(kp, (P){0, -1}), d.step+1} );
			Q.push( (data){ move(tp, (P){0, -1}), move(kp, (P){0, 1}), d.step+1} );
			Q.push( (data){ move(tp, (P){1, 0}), move(kp, (P){-1, 0}), d.step+1} );
			Q.push( (data){ move(tp, (P){-1, 0}), move(kp, (P){1, 0}), d.step+1} );
		}
		if (ans < 0) cout << "NA" << endl;
		else cout << ans << endl;
	}
}