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 now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if ans <= now.Turn {
			continue
		}

		if _, ok := memo[now.Person]; ok {
			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++
			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 <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <utility>
#include <functional>
#include <sstream>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <climits>
#include <fstream>
using namespace std;
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v;}
template<class T> inline string toStr(T x) { ostringstream sout; sout << x; return sout.str();}
typedef vector<int> vi;
typedef vector<vi>  vvi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef long long ll;
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define REP(i,n) FOR(i,0,(n)-1)
const double EPS = 1e-12;
const double PI = acos(-1.0);
const int INF = INT_MAX/10;

typedef vector<vvi> vvvi;

int tdx[] = {1, 0, -1, 0};
int tdy[] = {0, 1, 0, -1};
int kdx[] = {-1, 0, 1, 0};
int kdy[] = {0, -1, 0, 1};

struct state {
	int tx, ty, kx, ky;
	state(int tx, int ty, int kx, int ky) : tx(tx), ty(ty), kx(kx), ky(ky) {};
};

int main() {
	int X, Y;
	while(cin >> X >> Y, X) {
		int tx, ty, kx, ky;
		cin >> tx >> ty >> kx >> ky;
		vvi field(Y, vi(X));
		REP(i, Y) {
			REP(j, X) {
				cin >> field[i][j];
			}
		}

		vector<vvvi> visited(Y, vvvi(X, vvi(Y, vi(X))));
		queue<state> Q;
		Q.push(state(tx-1, ty-1, kx-1, ky-1));
		int before, ans = -1;
		while(!Q.empty()) {
			state st = Q.front();
			Q.pop();

			before = visited[st.ky][st.kx][st.ty][st.tx];
			if(100 <= before) {
				continue;
			}
			if(st.kx == st.tx && st.ky == st.ty) {
				ans = before;
				break;
			}
			
			int ntx, nty, nkx, nky;
			REP(d, 4) {
				nkx = st.kx + kdx[d];
				nky = st.ky + kdy[d];
				ntx = st.tx + tdx[d];
				nty = st.ty + tdy[d];

				if(nkx<0 || X<=nkx || nky<0 || Y<=nky || field[nky][nkx]) {
					nkx = st.kx;
					nky = st.ky;
				}
				if(ntx<0 || X<=ntx || nty<0 || Y<=nty || field[nty][ntx]) {
					ntx = st.tx;
					nty = st.ty;
				}

				if(!visited[nky][nkx][nty][ntx]) {
					visited[nky][nkx][nty][ntx] = before + 1;
					Q.push(state(ntx, nty, nkx, nky));
				}
			}
		}

		if(ans == -1) {
			cout << "NA" << endl;
		} else {
			cout << ans << endl;
		}
	}
	return 0;
}

C++: #include <cstdio>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <utility>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <functional>
#include <sstream>

using namespace std;

#define fst first
#define scd second
#define pb push_back
#define mp make_pair
#define chmin(a,b) a=min(a,b)
#define chmax(a,b) a=max(a,b)
#define rep(i,x) for(int i=0;i<(int)x;++i)
#define rep1(i,x) for(int i=1;i<=(int)x;++i)
#define rrep(i,x) for(int i=(int)x-1;i>=0;--i)
#define rrep1(i,x) for(int i=(int)x;i>=1;--i)
#define repf(i,a,x) for(int i=a;i<(int)x;++i)
#define repf1(i,a,x) for(int i=a;i<=(int)x;++i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()

template<typename T> T get(){T a;cin >> a;return a;}
template<typename T> T rev(T & a){reverse(all(a));return a;}

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

const int inf = 1e9;
const ll linf = 1e18;

class P {
public:
    int x, y;
    P () {
        x = y = 0;
    };
    P (int x0,int y0) {
        x=x0,y=y0;
    };
};

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

int d[52][52];
int memo[52][52];
P coords[52][52];
bool used[52][52];

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int X, Y;
    while (cin >> X >> Y, X || Y) {
        int tx, ty; cin >> tx >> ty;
        int kx, ky; cin >> kx >> ky;
        fill(d[0], d[Y+2], 1);
        rep1(i, Y) rep1(j, X) cin >> d[i][j];

        queue<pair<P, P> > q;

        q.push(mp(P(tx, ty), P(kx, ky)));
        memo[ty][tx] = 0;

        int cnt = 0;

        while (q.size()) {
            if (cnt == 100) {
                break;
            }

            pair<P, P> r = q.front(); q.pop();
            P f = r.fst, s = r.scd;
            if (f.x == s.x && f.y == s.y) {
                cout << memo[r.fst.y][r.fst.x] << endl;
                goto nxt;
            }
            //if (used[f.y][f.x]) continue;
            //used[f.y][f.x] = true;

            rep(i, 4) {
                int nfx = f.x + dx[i], nfy = f.y + dy[i];
                int nsx = s.x - dx[i], nsy = s.y - dy[i];
                if (d[nfy][nfx] == 1 || d[nsy][nsx] == 1) continue;
                memo[nfy][nfx] = memo[f.y][f.x] + 1;
                q.push(mp(P(nfx, nfy), P(nsx, nsy)));
            }

            cnt++;
        }

        cout << "NA" << endl;

nxt:;
    }
}