Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
	)

var scanner = bufio.NewScanner(os.Stdin)

const INF = 0x7FFFFFFF

var (
	direction1 = [][]int{ // 奇数段目の移動方向
		{-1, 0}, {1, 0}, {0, -1}, {0, 1}, {1, -1}, {1, 1},
	}
	direction2 = [][]int{ // 偶数段目の移動方向
		{-1, -1}, {0, -1}, {1, 0}, {0, 1}, {-1, 1}, {-1, 0},
	}
)

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		m, _ := strconv.Atoi(buf[0])
		n, _ := strconv.Atoi(buf[1])
		if m == 0 && n == 0 {
			break
		}
		// initialize district_map
		/*
			district_map = [
				[-1, -1,  -1,  -1,  -1]
				[-1, INF, INF, INF, -1]
				[-1, INF, INF, INF, -1]
				[-1, INF, INF, INF, -1]
				[-1, INF, INF, INF, -1]
				[-1, -1,  -1,  -1,  -1]
			]
		*/
		district_map := make([][]int, n+2)
		for i := range district_map {
			district_map[i] = make([]int, m+2)
		}
		tmp1 := make([]int, m+2)
		for i := range tmp1 {
			tmp1[i] = -1
		}
		district_map[0] = tmp1
		district_map[n+1] = tmp1
		for i := 1; i < n+1; i++ {
			district_map[i] = make([]int, m+2)
			district_map[i][0] = -1
			district_map[i][m+1] = -1
			for j := 1; j < m+1; j++ {
				district_map[i][j] = INF
			}
		}

		scanner.Scan()
		s, _ := strconv.Atoi(scanner.Text())
		for i := 0; i < s; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			x, _ := strconv.Atoi(buf_[0])
			y, _ := strconv.Atoi(buf_[1])
			Search(Point{x, y}, district_map, m, n)
		}
		ans := 0
		scanner.Scan()
		t, _ := strconv.Atoi(scanner.Text())
		for i := 0; i < t; i++ {
			scanner.Scan()
			buf__ := strings.Split(scanner.Text(), " ")
			x, _ := strconv.Atoi(buf__[0])
			y, _ := strconv.Atoi(buf__[1])
			z := Count(Point{x, y}, district_map, m, n)
			ans = max(ans, z)
		}
		fmt.Println(ans)
	}
}

func max(a, b int) int {
	if a < b {
		return b
	}
	return a
}

type Point struct {
	x, y int
}

type Entry struct {
	hop   int
	point Point
}

func Search(p Point, mp [][]int, m, n int) {
	que := make([]Entry, 0)
	que = append(que, Entry{0, p})
	check := make([][]bool, n+2)
	for i := range check {
		check[i] = make([]bool, m+2)
	}
	check[p.y][p.x] = true
	mp[p.y][p.x] = 0
	var direction [][]int
	for len(que) > 0 {
		tmp := que[0]
		que = que[1:]
		dist, point := tmp.hop, tmp.point
		if point.y%2 == 0 {
			direction = direction1
		} else {
			direction = direction2
		}
		for _, d := range direction {
			nx, ny := point.x+d[0], point.y+d[1]
			if !check[ny][nx] && mp[ny][nx] != -1 {
				check[ny][nx] = true
				if mp[ny][nx] > dist+1 {
					mp[ny][nx] = dist + 1
				}
				que = append(que, Entry{dist + 1, Point{nx, ny}})
			}
		}
	}
}

func Count(p Point, mp [][]int, m, n int) int {
	que := make([]Entry, 0)
	que = append(que, Entry{0, p})
	check := make([][]bool, n+2)
	for i := range check {
		check[i] = make([]bool, m+2)
	}
	check[p.y][p.x] = true
	ans := 1
	var direction [][]int
	for len(que) > 0 {
		tmp := que[0]
		que = que[1:]
		dist, point := tmp.hop, tmp.point
		if point.y%2 == 0 {
			direction = direction1
		} else {
			direction = direction2
		}
		for _, d := range direction {
			nx, ny := point.x+d[0], point.y+d[1]
			if !check[ny][nx] && mp[ny][nx] != -1 {
				check[ny][nx] = true
				if mp[ny][nx] > dist+1 {
					ans++
				}
				que = append(que, Entry{dist + 1, Point{nx, ny}})
			}
		}
	}
	return ans
}

C++: #include<iostream>
#include<queue>

#define INV (-1)
#define MAX 128
#define MAX_ENEMY 10
#define MAX_STORE 21

using namespace std;

const int even_di[] = {-1,-1,0,0,1,1};
const int even_dj[] = {0,1,-1,1,0,1};
const int odd_di[] = {-1,-1,0,0,1,1};
const int odd_dj[] = {-1,0,-1,1,-1,0};
const int infty = 1 << 26;

class Area{
 public:
  int store;
  int dist[MAX_STORE];
  bool valid;
  Area():store(INV),valid(false){
    for(int i = 0; i < MAX_STORE; ++i){
      dist[i] = infty;
    }
  }
};

class Map{
 public:
  int n,m;
  Area T[MAX][MAX];
  Map(){}
  Map(int n, int m):n(n),m(m){
    for(int i = 1; i < n+1; ++i){
      for(int j = 1; j < m+1; ++j){
	T[i][j].valid = true;
	for(int k = 0; k < MAX_STORE; ++k){
	  T[i][j].dist[k] = infty;
	}
      }
    }
  }
  int occupied(int store){
    int ret = 0;
    for(int i = 1; i < n + 1; ++i){
      for(int j = 1; j < m + 1; ++j){
	int minimum = infty;
	int id = -1;
	int cnt = 0;
	for(int k = 0; k < MAX_STORE; ++k){
	  //if( k >= MAX_ENEMY && k != store ) continue;
	  minimum = min( minimum, T[i][j].dist[k] ); 
	}
	for(int k = 0; k < MAX_STORE; ++k){
	  //if( k >= MAX_ENEMY && k != store ) continue;
	  if( minimum == T[i][j].dist[k] ){
	    ++cnt;
	    id = k;
	  }
	}
	if( cnt == 1 && id == store ){
	  ++ret;
	}
      }
    }
    return ret;
  }
};

class State
{
public:
  int i,j;
  int cost;
  State():i(0),j(0),cost(infty){}
  State(int i, int j, int cost):i(i),j(j),cost(cost){}
};
  
void store_bfs( int i, int j, int store, Map &M )
{
  queue< State > qpi;
  
  qpi.push( State(i,j,0) );
  while(!qpi.empty()){
    State now = qpi.front();
    qpi.pop();
    
    // if( M.T[now.i][now.j].dist[store] < infty ) continue;
    M.T[now.i][now.j].dist[store] = now.cost;
    
    for(int i = 0; i < sizeof(even_di)/sizeof(*even_di); ++i){
      int ti = now.i + ( now.i%2==0 ? even_di[i] : odd_di[i] );
      int tj = now.j + ( now.i%2==0 ? even_dj[i] : odd_dj[i] );
      
      if( !M.T[ti][tj].valid ) continue;
      if( M.T[ti][tj].dist[store] < infty ) continue;
      // M.T[ti][tj].dist[store] = now.cost+1;
      
      qpi.push( State(ti,tj,now.cost+1) );
    }
  }
}

int main()
{
  while(true){
    int m,n;
    int ans = 0;
    cin >> m;
    if( m == 0 ) break;
    cin >> n;
    if( n == 0 ) break;
    int st;
    Map M(n,m);
    
    cin >> st;
    for(int i = 0; i < st; ++i){
      int y,x;
      cin >> x >> y;
      //++x;++y;
      M.T[y][x].store = i;
      store_bfs( y, x, i, M );
    }
    
    int cands;
    cin >> cands;
    for(int i = 0; i < cands; ++i){
      int y,x;
      cin >> x >> y;
      //++x;++y;
      M.T[y][x].store = MAX_ENEMY + i;
      store_bfs( y, x, MAX_ENEMY+i, M );
    }
    

    /*
    for(int i = 0; i < n+2; ++i){
      for(int j = 0; j < m+2; ++j){
	cout << "(" << j << " , " << i << ") = ";
	for(int k = 0; k < MAX_STORE; ++k){
	  cout << M.T[i][j].dist[k] << ' ';
	}
	cout << endl;
      }
      cout << "--------" << endl;
    }
    */
    

    for(int i = 0; i < cands; ++i){
      ans = max( ans, M.occupied( MAX_ENEMY + i ) );
    }

    cout << ans << endl;
    
  }
  return 0;

}

C++: #include <iostream>
#include <cmath>
using namespace std;

#define INF (1<<20)
int field[128][128];

int dist(int x1, int y1, int x2, int y2)
{
	x1-=(y1-1)/2;
	x2-=(y2-1)/2;

	return (abs(x1-x2)+abs(y1-y2)+abs((x1+y1)-(x2+y2)))/2;
}

int main()
{
	int w,h,n,x0,y0,cnt,ans;
	while(cin >> w, w)
	{
		cin >> h;
		for(int y=1; y<=h; y++)
		for(int x=1; x<=w; x++)
		{
			field[y][x] = INF;
		}
		
		cin >> n;
		while(n--)
		{
			cin >> x0 >> y0;
			for(int y=1; y<=h; y++)
			for(int x=1; x<=w; x++)
			{
				field[y][x] = min(field[y][x],dist(x0,y0,x,y));
			}
		}

		ans = 0;
		cin >> n;
		while(n--)
		{
			cnt = 0;
			cin >> x0 >> y0;
			for(int y=1; y<=h; y++)
			for(int x=1; x<=w; x++)
			{
				if(field[y][x]>dist(x0,y0,x,y)) cnt++;
			}
			ans = max(ans,cnt);
		}
		cout << ans << endl;
	}
	return 0;
}