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>
#include<algorithm>

using namespace std;

typedef pair<int, int> P;
typedef pair<int, P> PP;

int m, n, s, t;//?¨????????????¢?¨??????????????????°?¨?????????°
int dis[100][100];//???????¨?
const int vx1[6] = { -1,-1,0,1,0,-1 };//?????????????\???°??¨???????????¶??°??¨
const int vx2[6] = { -1,0,1,1,1,0 };//??????????????¶??°??¨??????????\???°??¨
const int vy[6] = { 0,-1,-1,0,1,1 };
P store[10], plan[10];

void bfs() {
	queue<PP> q;//????????????????????§?¨?????????§?¨?
	for (int i = 0; i < s; i++) {
		q.push(make_pair(0, make_pair(store[i].first, store[i].second)));
		dis[store[i].first][store[i].second] = -1;//?????§???????????¨?????????-1??¨??????
	}
	while (q.size()) {
		int ct = q.front().first;
		P tmp = q.front().second;
		q.pop();
		for (int i = 0; i < 6; i++) {
			int fy = tmp.first, fx = tmp.second;
			if (fy % 2)fx += vx2[i];
			else fx += vx1[i];
			fy += vy[i];
			if (fy < 0 || fy >= m || fx < 0 || fx >= n)continue;
			if (!dis[fy][fx]) {
				dis[fy][fx] = ct + 1;
				q.push(make_pair(ct + 1, make_pair(fy, fx)));
			}
		}
	}
}

int bfs2(int a) {
	int ans = 1;
	queue<PP> q;
	q.push(make_pair(0, plan[a]));
	bool islook[100][100] = {};
	bool f = false;
	for (int i = 0; i < s; i++) {
		if (plan[a] == store[i])f = true;
	}
	if (f)return 0;
	islook[q.front().second.first][q.front().second.second] = true;
	while (q.size()) {
		P tmp = q.front().second;
		int ct = q.front().first;
		q.pop();
		for (int i = 0; i < 6; i++) {
			int fy = tmp.first, fx = tmp.second;
			if (fy % 2)fx += vx2[i];
			else fx += vx1[i];
			fy += vy[i];
			if (fy < 0 || fy >= m || fx < 0 || fx >= n)continue;
			if (!islook[fy][fx] && dis[fy][fx] - ct > 1) {
				ans++;
				dis[fy][fx] = true;
				q.push(make_pair(ct + 1, make_pair(fy, fx)));
			}
		}
	}
	return ans;
}

int main() {
	while (cin >> m >> n, m * n) {
		cin >> s;
		for (int i = 0; i < s; i++) {
			cin >> store[i].second >> store[i].first;
			store[i].first--, store[i].second--;
		}
		cin >> t;
		for (int i = 0; i < t; i++) {
			cin >> plan[i].second >> plan[i].first;
			plan[i].first--, plan[i].second--;
		}
		bfs();//?????????????????????????????¢?????¬???
		int ans = 0;
		for (int i = 0; i < t; i++) {
			ans = max(bfs2(i), ans);//??¨????£???°?????????
		}
		cout << ans << endl;
		for (int i = 0; i < n; i++)for (int j = 0; j < m; j++)dis[i][j] = 0;
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<cassert>
#include<vector>
#include<deque>
using namespace std;
typedef pair<int,int> P;
int n,m,cnt;
int mincost[110][110];
bool visited[110][110];
int dx[2][6] = {{-1,+0,1,0,-1,-1},{+0,+1,1,1,0,-1}};
int dy[2][6] = {{-1,-1,0,1,+1,+0},{-1,-1,0,1,1,+0}};
bool f;
 
void dfs(int x,int y,int cost)
{
  //if(!f)
  //cout << "xy = "  << x << "," << y << " cost = " << cost << endl;
  for(int i=0;i<6;i++)
    {
      int nx = x + dx[y%2][i];
      int ny = y + dy[y%2][i];
      if(!(0 <= nx && nx < m && 0 <= ny && ny < n))
    continue;
      //if(!f)cout << "mincost["<<ny<<"]["<<nx<<"] = " << mincost[ny][nx] << " = cost + 1  = " << cost + 1  << endl;
      if(mincost[ny][nx] > cost+1)
    {
      if(!visited[ny][nx])
        cnt++;
      visited[ny][nx] = true;
      mincost[ny][nx] = cost + 1;
      dfs(nx,ny,cost+1);
    }
    }
}
 
int main()
{
  while(true)
    {
      cin >> m;
      if(!m) break;
      cin >> n;
      for(int i=0;i<n;i++) 
    for(int j=0;j<m;j++)
      mincost[i][j] = (1<<29);  
      f = true;
      int s,t,mex = 0;
      scanf("%d",&s);
      for(int i=0;i<s;i++)
    {
      int x,y;
      scanf("%d %d",&x,&y);
      x--,y--;
      mincost[y][x] = 0;
      dfs(x,y,0);
    }
      f = false;
      scanf("%d",&t);
      for(int i=0;i<t;i++)
    {   
      int pre_mincost[n][m];
      for(int j=0;j<n;j++)
        for(int k=0;k<m;k++)
          pre_mincost[j][k] = mincost[j][k],visited[j][k] = false;
      int p,q;
      scanf("%d %d",&p,&q);
 
      cnt = 1,p--,q--;
      mincost[q][p] = 0,visited[q][p] = true;
       
      dfs(p,q,0);
       
      mex = max(mex,cnt);
      for(int j=0;j<n;j++)
        for(int k=0;k<m;k++)
          mincost[j][k] = pre_mincost[j][k];
    }
      cout << mex << endl;
    }
  return 0;
}