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)
	pq = append(pq, 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)
		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 += 1
			if next.Turn < 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				pq = append(pq, 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++: 
#include<cstdio>
#include <queue>
#include <utility>
#include <cstring>
#include <vector>

using namespace std;

int brd[55][55];
int inpb[55][55];
int ta,yo,x1,x2,y1,y2,i,j;
int tyux,tyuy;

/*
typedef struct{
int xx;
int yy;
}zah;
*/
typedef pair<int,int> zah;
typedef pair<int,zah> mp;

int muki[4][2]={
	{1,0},
	{0,1},
	{-1,0},
	{0,-1}
};


int main(void){

while(1){
scanf("%d%d",&yo,&ta);
if(yo==0)break;
scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
memset(inpb,-1,sizeof(inpb));
memset(brd,-1,sizeof(brd));
for(j=1;j<=ta;j++){
for(i=1;i<=yo;i++){
scanf("%d",&(inpb[i][j]));
brd[i][j]=inpb[i][j];
}
}


if(x1%2!=x2%2 || y1%2!=y2%2){
printf("NA\n");
continue;
}
tyux=(x1+x2)/2;
tyuy=(y1+y2)/2;

int x,y;
for(i=1;i<=yo;i++){
for(j=1;j<=ta;j++){
x=tyux*2-i;y=tyuy*2-j;
if(x>0 && x<=yo && y>0 && y<=ta){
if(brd[x][y]==0){
brd[x][y]=inpb[i][j];
}
}
}
}


mp pa,pb;
pa.first=0;
pa.second.first=x1;
pa.second.second=y1;
priority_queue<mp,vector<mp>,greater<mp> > qu;

qu.push(pa);

int bol[55][55]={};
bol[x1][y1]=1;
int cl=0;
while(!qu.empty()){
	pa=qu.top();
//printf("      %d %d %d\n",pa.second.first,pa.second.second,pa.first);
	qu.pop();
	if(pa.first>=100){
		break;
	}
	if(pa.second.first==tyux && pa.second.second==tyuy){
		printf("%d\n",pa.first);
		cl=1;
		break;
	}
	for(i=0;i<4;i++){
		x=pa.second.first+muki[i][0];
		y=pa.second.second+muki[i][1];
//printf("                %d %d %d\n",x,y,bol[x][y]);
		if(brd[x][y]==0 && bol[x][y]==0){
			bol[x][y]=1;
			pb.first=pa.first+1;
			pb.second.first=x;
			pb.second.second=y;
			qu.push(pb);
		}
	}
}
if(cl==0){
	printf("NA\n");
}
}
return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

int table[51][51];

bool memo[51][51][51][51];

int main() {

    while(1){

        int w,h;

        scanf(" %d %d",&w,&h);

        if(w==0&&h==0) break;

        int tx,ty,kx,ky;

        scanf(" %d %d %d %d",&tx,&ty,&kx,&ky);

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

        for(int i=0;i<51;i++){
            for(int j=0;j<51;j++){
                table[i][j] = 1;
                for(int k=0;k<51;k++){
                    for(int r=0;r<51;r++){
                        memo[i][j][k][r] = false;

                    }
                }
            }
        }

        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                scanf(" %d",&table[i][j]);
            }
        }

        //memset(memo,false,sizeof(memo));

        queue<vector<int> > q;

        vector<int> v(5);

        v[0] = tx; v[1] = ty; v[2] = kx; v[3] = ky; v[4] = 0;

        q.push(v);

        bool check = false;

        while(!q.empty()){

            v = q.front(); q.pop();

            if(v[4] >= 100){
                break;
            }

            if(memo[v[0]][v[1]][v[2]][v[3]]){
                continue;
            }

            if(v[0] >= w || v[1] >= h || v[2] >= w || v[3] >= h || v[0] < 0 || v[1] < 0 || v[2] < 0 || v[3] < 0 || table[v[0]][v[1]] == 1 || table[v[2]][v[3]] == 1){
                continue;
            }

            if(v[0] == v[2] && v[1] == v[3]){
                check = true;
                printf("%d\n",v[4]);
                break;
            }

            memo[v[0]][v[1]][v[2]][v[3]] = true;

            v[4]++;

            tx = v[0]; ty = v[1]; kx = v[2]; ky = v[3];

            tx++; kx--;

            v[0] = tx; v[1] = ty; v[2] = kx; v[3] = ky;

            q.push(v);

            tx--; kx++;

            tx--; kx++;

            v[0] = tx; v[1] = ty; v[2] = kx; v[3] = ky;

            q.push(v);

            tx++; kx--;

            ty--; ky++;

            v[0] = tx; v[1] = ty; v[2] = kx; v[3] = ky;

            q.push(v);

            tx = v[0]; ty = v[1]; kx = v[2]; ky = v[3];

            ty++; ky--;

            ty++; ky--;

            v[0] = tx; v[1] = ty; v[2] = kx; v[3] = ky;

            q.push(v);

            /*if(v[0] >= w || v[1] >= h || v[2] >= w || v[3] >= h || v[0] < 0 || v[1] < 0 || v[2] < 0 || v[3] < 0 || table[v[0]][v[1]] == 1 || table[v[2]][v[3]] == 1){

            }else {
                q.push(v);
            }*/



        }

        if(!check){
            printf("NA\n");
        }



    }

    return 0;
}