Go: package main

import (
	"container/heap"
	"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)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		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 < 100-1 {
				heap.Push(&pq, next)
			}
		}
	}
	fmt.Println("NA")
}

func main() {
	var h, w int64
	for {
		fmt.Scan(&h, &w)
		if h == 0 && w == 0 {
			break
		}
		solve(h, w)
	}
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <cstring>

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define INF 1<<30

using namespace std;

int dx[4] = {1,0,-1,0};
int dy[4] = {0,1,0,-1};

struct Data
{
	int tx,ty,kx,ky,cost;

	Data(int tx,int ty,int kx,int ky,int cost) : tx(tx),ty(ty),kx(kx),ky(ky),cost(cost) {}
};

int main()
{
	int x,y;
	while(cin >> x >> y)
	{
		if(x == 0 && y == 0) break;

		int tx,ty,kx,ky;
		cin >> tx >> ty >> kx >> ky;

		tx--;
		ty--;
		kx--;
		ky--;

C++: #include <iostream>
#include <vector>
#include <stack>
#include <string>
#include <queue>
#include <sstream>
#include <cstdlib>
#include <cstdio>
#include <map>
using namespace std;
typedef long long ll;

int x, y;
int time[51][51][51][51];
char field[51][51];
int dx[] = {
	0, -1, 0, 1
};
int dy[] = {
	1, 0, -1, 0
};
struct twins{
	int x1;
	int y1;
	int x2; 
	int y2;
};

bool can_move(int x1, int y1){
	if(x1 > 0 && x1 <= x && y1 > 0 && y1 <= y){
		if(field[y1][x1] == '0') return true;
		else return false;
	}
	return false;
}

void get_time(int x1, int y1, int x2, int y2){
	twins t0;
	t0.x1 = x1, t0.x2 = x2, t0.y1 = y1, t0.y2 = y2;
	queue<twins> qt;
	qt.push(t0);
	while(!qt.empty()){
		twins t = qt.front(); qt.pop();
		for(int i = 0; i < 4; i++){
			int ay = t.y1 + dy[i];
			int ax = t.x1 + dx[i];
			int by = t.y2 - dy[i];
			int bx = t.x2 - dx[i];
			if(!can_move(ax, ay)){
				ay = t.y1;
				ax = t.x1;
			}
			if(!can_move(bx, by)){
				by = t.y2;
				bx = t.x2;
			}
			if(time[ay][ax][by][bx] < 0 || time[ay][ax][by][bx] > time[t.y1][t.x1][t.y2][t.x2] + 1){
				time[ay][ax][by][bx] = time[t.y1][t.x1][t.y2][t.x2] + 1;
				t0.x1 = ax, t0.x2 = bx, t0.y1 = ay, t0.y2 = by;
				qt.push(t0);
			}
		}
	}
}

int main(){
	int ax, ay, bx, by;
	while(cin >> x >> y && (x || y)){
		int count = 101;
		memset(time, -1, sizeof(time));
		cin >> ax >> ay >> bx >> by;
		for(int i = 1; i <= y; i++){
			for(int j = 1; j <= x; j++){
				cin >> field[i][j];
			}
		}
		time[ay][ax][by][bx] = 0;
		get_time(ax, ay, bx, by);
		for(int i = 1; i <= y; i++){
			for(int j = 1; j <= x; j++){
				if(time[i][j][i][j] >= 0) count = min(count, time[i][j][i][j]);
			}
		}
		if(count == 101) cout << "NA" << endl;
		else cout << count << endl;
	}
	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define fi first
#define sc second
#define pb push_back
typedef pair<int,int> P;
typedef pair<P,P> PP;
typedef pair<int,PP> PPP;
int dx[4]={-1,0,0,1};
int dy[4]={0,-1,1,0};
int S[51][51][51][51];
int main()
{
	while(true){
		int X,Y;
		int tx;int ty;
		int kx;int ky;
		scanf("%d%d",&X,&Y);
		if(X==0&&Y==0)break;
		scanf("%d%d%d%d",&tx,&ty,&kx,&ky);tx--;ty--;kx--;ky--;
		int grid[51][51];
		for(int i=0;i<Y;i++){
			for(int j=0;j<X;j++){
				scanf("%d",&grid[i][j]);
			}
		}
		
		for(int i=0;i<Y;i++){
			for(int j=0;j<X;j++){
				for(int k=0;k<Y;k++){
					for(int l=0;l<X;l++){
						S[i][j][k][l]=1001;
					}
				}
			}
		}
		
		priority_queue<PPP>s;
		PP x;x.fi.sc=tx;x.fi.fi=ty;x.sc.sc=kx;x.sc.fi=ky;
		s.push(PPP(0,x));
		
		while(!s.empty()){
			PPP p=s.top();s.pop();
			if(S[p.sc.fi.fi][p.sc.fi.sc][p.sc.sc.fi][p.sc.sc.sc]<=p.fi)continue;
			S[p.sc.fi.fi][p.sc.fi.sc][p.sc.sc.fi][p.sc.sc.sc]=p.fi;
			if(p.fi==100)continue;
			for(int k=0;k<4;k++){
				PP t;
				if(p.sc.fi.fi+dy[k]<0||p.sc.fi.fi+dy[k]>=Y||p.sc.fi.sc+dx[k]<0||p.sc.fi.sc+dx[k]>=X){
					t.fi.fi=p.sc.fi.fi;t.fi.sc=p.sc.fi.sc;
				}
				else if(grid[p.sc.fi.fi+dy[k]][p.sc.fi.sc+dx[k]]==1){
					t.fi.fi=p.sc.fi.fi;t.fi.sc=p.sc.fi.sc;
				}
				else{
					t.fi.sc=p.sc.fi.sc+dx[k];t.fi.fi=p.sc.fi.fi+dy[k];
				}
				if(p.sc.sc.fi-dy[k]<0||p.sc.sc.fi-dy[k]>=Y||p.sc.sc.sc-dx[k]<0||p.sc.sc.sc-dx[k]>=X){
					t.sc.sc=p.sc.sc.sc;t.sc.fi=p.sc.sc.fi;
				}
				else if(grid[p.sc.sc.fi-dy[k]][p.sc.sc.sc-dx[k]]==1){
					t.sc.sc=p.sc.sc.sc;t.sc.fi=p.sc.sc.fi;
				}
				else{
					t.sc.fi=p.sc.sc.fi-dy[k];t.sc.sc=p.sc.sc.sc-dx[k];
				}
				if(S[t.fi.fi][t.fi.sc][t.sc.fi][t.sc.sc]<=p.fi+1)continue;
				s.push(PPP(p.fi+1,t));
			}
		}
		int ans=1001;
		for(int i=0;i<Y;i++){
			for(int j=0;j<X;j++){
				ans=min(ans,S[i][j][i][j]);
				
			}
		}
		if(ans==1001)printf("NA\n");
		else printf("%d\n",ans);
		return 0;
	}
	return 0;
}