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<bits/stdc++.h>
using namespace std;
typedef pair<int,int> PA;
int dx[4] = {0,0,1,-1};
int dy[4] = {1,-1,0,0};
int main(){
  int w,h,tx,ty,kx,ky,ans;
  int de[55][55];
  queue<PA> que;
  while(cin >> w >> h,w!=0&&h!=0){
    cin >> tx >> ty >> kx >> ky;
    for(int i=1;i<=h;i++){
      for(int j=1;j<=w;j++){
	cin >> de[i][j];
      }
    }
    if( (tx+kx)%2 != 0 || (ty+ky)%2 != 0){
      puts("NA");
      continue;
    }
    que.push(PA(0,0));
    ans = 100;
    while(!que.empty()){
      PA p = que.front();
      que.pop();
      for(int i=0;i<4;i++){
	int y1 = ty + p.first + dy[i];
	int x1 = tx + p.second + dx[i];
	int y2 = ky - p.first - dy[i];
	int x2 = kx - p.second - dx[i];
	if(x1<=0||y1<=0||x1>w||y1>h||de[y1][x1]==1) continue;
	if(x2<=0||y2<=0||x2>w||y2>h||de[y2][x2]==1) continue;
	if(y1==y2&&x1==x2) ans = min(ans,abs(ty-y1)+abs(tx-x1));
	de[y1][x1] = 1;
	de[y2][x2] = 1;
	que.push(PA(p.first+dy[i],p.second+dx[i]));	
      }
    }
    if(ans == 100) puts("NA");
    else cout << ans << endl;
  }
  return(0);
}

C++: #include <bits/stdc++.h>
using namespace std;
#define MAX 50
#define INFTY (1<<10)
class State {
public:
	int ty, tx, ky, kx, t;
	State(int ty = 0, int tx = 0, int ky = 0, int kx = 0, int t = 0) :
			ty(ty), tx(tx), ky(ky), kx(kx), t(t) {
	}
	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 H, W, G[MAX][MAX];
bool isBlock(int y, int x) {
	if (0 > y || 0 > x || y >= H || x >= W)
		return true;
	return G[y][x];
}
int bfs(int ty, int tx, int ky, int kx) {
	queue<State> Q;
	map<State, bool> V;
	State start = State(ty, tx, ky, kx, 0);
	V[start] = true;
	Q.push(start);
	State u, v;
	const int dy[4] = { 0, -1, 0, 1 };
	const int dx[4] = { 1, 0, -1, 0 };
	int nty, ntx, nky, nkx;
	while (!Q.empty()) {
		u = Q.front();
		Q.pop();
		if (u.tx == u.kx && u.ty == u.ky)
			return u.t;
		for (int r = 0; r < 4; r++) {
			nty = u.ty + dy[r];
			ntx = u.tx + dx[r];
			nky = u.ky + dy[r] * (-1);
			nkx = u.kx + dx[r] * (-1);
			if (isBlock(nty, ntx)) {
				nty = u.ty;
				ntx = u.tx;
			}
			if (isBlock(nky, nkx)) {
				nky = u.ky;
				nkx = u.kx;
			}
			v = State(nty, ntx, nky, nkx);
			if (!V[v]) {
				v.t = u.t + 1;
				V[v] = true;
				Q.push(v);
			}
		}
	}
	return INFTY;
}
int main() {
	int tx, ty, kx, ky;
	while (cin >> W >> H && W) {
		cin >> tx >> ty >> kx >> ky;
		for (int i = 0; i < H; i++)
			for (int j = 0; j < W; j++)
				cin >> G[i][j];
		int t = bfs(ty - 1, tx - 1, ky - 1, kx - 1);
		if (t == INFTY)
			cout << "NA" << endl;
		else
			cout << t << endl;
	}
	return 0;
}

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

const int INF = 100;
const int MAX = 50;
const int dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1};
int field[MAX][MAX], cost[MAX][MAX][MAX][MAX];

typedef pair<int, int> P;
typedef pair<P, P> Q;
typedef pair<int, Q> S;

bool check(int x, int y, int w, int h)
{
    return(x >= 0 && x < w && y >= 0 && y < h && field[y][x] == 0);
}

int main()
{
    int w, h, tx, ty, kx, ky;
    while(cin >> w >> h && w) {

        cin >> tx >> ty >> kx >> ky;
        for(int i = 0; i < h; i++) {
            for(int j = 0; j < w; j++) {
                cin >> field[i][j];
                for(int k = 0; k < h; k++) 
                    for(int l = 0; l < w; l++)
                        cost[i][j][k][l] = INF;
            }
        }

        queue<S> que;
        int min = INF;
        que.push(S(0, Q( P(tx, ty), P(kx, ky))));
        //cost[tx][ty][kx][ky] = 0;
        while(!que.empty()) {
            S s = que.front(); que.pop();
            int x1, y1, x2, y2, step;
            step = s.first;
            x1 = s.second.first.first;
            y1 = s.second.first.second;
            x2 = s.second.second.first;
            y2 = s.second.second.second;
            
            cost[x1][y1][x2][y2] = step;

            if(x1 == x2 && y1 == y2) {
                min = step;
                break;
            }

            for(int k = 0; k < 4; k++) {
                int nx1, ny1, nx2, ny2;
                nx1 = x1 + dx[k];
                ny1 = y1 + dy[k];
                nx2 = x2 - dx[k];
                ny2 = y2 - dy[k];
                if(!check(nx1, ny1, w, h) || ! check(nx2, ny2, w, h) || cost[nx1][ny1][nx2][ny2] <= step + 1)
                    continue;
                que.push(S(step + 1, Q(P(nx1, ny1), P(nx2, ny2))));
            }
        }
        if(min == INF)
            cout << "NA" << endl;
        else 
            cout << min << endl;
    }
    
}