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++: //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;
	}
}

C++: #include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<complex>
#include<cmath>
#include<algorithm>
#include<map>
#include<vector>
#include<sstream>
#include<queue>
#include<iostream>
using namespace std;
struct data{
    int x;
    int y;
    int u;
    int v;
    int t;
};

bool vis[60][60][60][60] = {};
const int dx[] = {1,0,-1,0},dy[] = {0,1,0,-1};
int main(void){
    int w,h;
    while(cin>>w>>h,w){
        int x,y,u,v;
        cin>>x>>y>>u>>v;
        bool screen[60][60] = {};
        for(int i = 0;i < h;i++){
            for(int j = 0;j < w;j++){
                cin>>screen[i][j];
            }
        }
        data D;
        D.x = x,D.y = y;
        D.u = u,D.v = v;
        D.t = 0;
        queue<data> Q;
        Q.push(D);

        while(!Q.empty()){
            data E = Q.front();Q.pop();

            vis[E.x][E.y][E.u][E.v] = true;
            vis[E.u][E.v][E.x][E.y] =true;
            if(E.x == E.u&&E.y == E.v){
                cout<<E.t<<endl;
                goto e;
            }
            for(int i = 0;i < 4;i++){
                if(0<=E.x+dx[i]&&E.x+dx[i]<w&&0<=E.y+dy[i]&&E.y+dy[i]<h&&
                   0<=E.u+dx[(i+2)%4]&&E.u+dx[(i+2)%4]<w&&0<=E.v+dy[(i+2)%4]&&E.v+dy[(i+2)%4]<h){

                    data F = E;
                    F.t++;
                    F.x+=dx[i],F.y+=dy[i],F.u+=dx[(i+2)%4],F.v+=dy[(i+2)%4];
                    if(!vis[F.x][F.y][F.u][F.v]&&!vis[F.u][F.v][F.x][F.y]&&!screen[F.x][F.y]&&!screen[F.u][F.v]){
                        Q.push(F);
                    }
                }
            }

        }
        cout<<"NA"<<endl;
        e:;
    }


    return 0;
}