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<iostream>
#include<utility>
#include<queue>
#include<map>
using namespace std;
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
int main() {
	int W, H, tx, ty, kx, ky;
	bool d[52][52];
	map<pair<pair<int, int>, pair<int, int> >,bool> m;
	pair<pair<int, int>, pair<int, int> >num;
	pair<pair<int, int>, pair<int, int> >copy;
	while (true) {
		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.first.first = tx;
		num.first.second = ty;
		num.second.first = kx;
		num.second.second = ky;
		queue<pair<pair<int, int>, pair<int, int> > > q;
		q.push(num);
		int qsize = q.size();
		int loopcount = 0;
		while (!q.empty()) {
			num = q.front();
			q.pop();
			if (qsize == 0) {
				qsize = q.size()+1;
				loopcount++;
				if (loopcount == 100) {
					cout << "NA" << endl;
					break;
				}
			}
			qsize--;
			cerr << num.first.first << " " << num.first.second << " : " << num.second.first << " " << num.second.second << " : " << loopcount << endl;
			if (num.first.first == num.second.first && num.first.second == num.second.second) {
				cout << loopcount << endl;
				break;
			}
			for (int i = 0; i < 4; i++) {
				copy.first.first = num.first.first+dx[i];
				copy.first.second = num.first.second+dy[i];
				if (d[copy.first.first][copy.first.second]) {
					copy.first.first -= dx[i];
					copy.first.second -= dy[i];
				}
				copy.second.first =num.second.first-dx[i];
				copy.second.second =num.second.second- dy[i];
				if (d[copy.second.first][copy.second.second]) {
					copy.second.first += dx[i];
					copy.second.second += dy[i];
				}
				if (!m[copy]) {
					m[copy] = true;
					q.push(copy);
				}
			}
			if (q.empty()) {
				cout << "NA" << endl;
			}
		}
	}
	return 0;
}

C++: #include<iostream>
#include<string>
#include<cstdio>
#include<algorithm>
#include<queue>
#define P pair<int,int>
using namespace std;

bool c[52][52];
int d[52][52];
int x[4] = { -1,0,0,1 }, y[4] = { 0,-1,1,0 };
int main() {
	int a, b;
	while (cin >> a >> b, a | b) {
		memset(c, true, sizeof(c));
		memset(d,-1,sizeof(d));
		int e, f, g, h; cin >> e >> f >> g >> h;
		for (int i = 0; i < b; i++) {
			for (int j = 0; j < a; j++) {
				cin >> c[j + 1][i + 1];
			}
		}
		if (((e + g) & 1) == ((f + h) & 1)) {
		queue<P>Q;
		Q.push(P(e,f));
		d[e][f] = 0;
		while (Q.size()) {
			P o = Q.front(); Q.pop();
			for (int i = 0; i < 4; i++) {
				if (!c[o.first + x[i]][o.second + y[i]]&&!c[e+g-(o.first + x[i])][f+h-(o.second + y[i])]&& d[o.first + x[i]][o.second + y[i]] ==-1) {
					d[o.first + x[i]][o.second + y[i]] = d[o.first][o.second] + 1;
					Q.push(P(o.first + x[i], o.second + y[i]));
				}
			}
		}
		if (d[(e + g) / 2][(f + h) / 2] == -1|| d[(e + g) / 2][(f + h) / 2]>99)puts("NA");
		else cout << d[(e + g) / 2][(f + h) / 2] << endl;
		}
		else puts("NA");
	}
}

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;
}