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 <complex>
#include <sstream>
#include <string>
#include <algorithm>
#include <deque>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <vector>
#include <set>
#include <limits>
#include <cstdio>
#include <cctype>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <ctime>
using namespace std;
#define REP(i, j) for(int i = 0; i < (int)(j); ++i)
#define FOR(i, j, k) for(int i = (int)(j); i < (int)(k); ++i)
#define SORT(v) sort((v).begin(), (v).end())
#define REVERSE(v) reverse((v).begin(), (v).end())
typedef pair<int, int> P;
typedef pair<int, P> PP;

int mx[2][6] = {
  {-1, 0, 1, 0, -1, -1},
  {0, 1, 1, 1, 0, -1}
};
int my[2][6] = {
  {1, -1, 0, 1, 1, 0},
  {-1, -1, 0, 1, 1, 0}
};

int W, H, S, T;

void update(int sy, int sx, vector< vector<int> > &v){
  queue<PP> open;
  open.push(PP(0, P(sy, sx)));
  v[sy][sx] = 0;
  while(!open.empty()){
    PP pp = open.front(); open.pop();
    int y = pp.second.first, x = pp.second.second, n = pp.first, t = (y % 2 == 0);
    REP(i, 6){
      int ny = y + my[t][i], nx = x + mx[t][i];
      if(ny <= 0 || nx <= 0 || ny > H || nx > W || v[ny][nx] <= n + 1) continue;
      v[ny][nx] = n + 1;
      open.push(PP(n + 1, P(ny, nx)));
    }
  }
}

int count(int y, int x, int n, vector< vector<int> > &v, vector< vector<bool> > &visited, bool f){
  int res = 1;
  if(!f && v[y][x] <= n) res = 0;
  int t = (y % 2 == 0);
  visited[y][x] = 1;
  REP(i, 6){
    int ny = y + my[t][i], nx = x + mx[t][i];
    if(ny <= 0 || nx <= 0 || ny > H || nx > W || v[ny][nx] <= n + 1 || visited[ny][nx]) continue;
    res += count(ny, nx, n + 1, v, visited, 1);
  }
  return res;
}

int main() {
  while(cin >>W >>H && W && H){
    vector< vector<int> > v(H + 1, vector<int>(W + 1, 1e9));
    cin >>S;
    REP(s, S){
      int x, y; cin >>x >>y;
      update(y, x, v);
    }
    cin >>T;
    int res = 0;
    REP(t, T){
      int x, y; cin >>x >>y;
      vector< vector<bool> > visited(H + 1, vector<bool>(W + 1, 0));
      res = max(res, count(y, x, 0, v, visited, 0));
    }
    cout <<res <<endl;
  }
  return 0;
}

C++: #include<iostream>
#include<queue>
#include<algorithm>
#include<vector>
#include<map>
using namespace std;
typedef pair < int , int > Pi;
typedef pair < int , Pi > Pii;
#define fr first
#define sc second

int m, n, s;
int min_cost[100][100];
bool used[100][100];
int dy[] = { -1, -1, 0, 1, 1, 0};
int dx[][6] = {{ -1, 0, 1, 0, -1, -1}, { 0, 1, 1, 1, 0, -1}};

bool isover(int y, int x){
  return y < 0 || y >= m || x < 0 || x >= n;
}

void bfs(int y, int x){
  queue< Pii > que;
  que.push(Pii( 0, Pi( y, x)));
  min_cost[y][x] = 0;
  while(!que.empty()){
    Pii p = que.front();
    que.pop();
    for(int i = 0 ; i < 6 ; i++ ){
      int ny = p.sc.fr + dy[i], nx = p.sc.sc + dx[p.sc.fr % 2][i];
      if(isover( ny, nx) || min_cost[ny][nx] < p.fr + 1) continue;
      que.push(Pii( p.fr + 1, Pi( ny, nx)));
      min_cost[ny][nx] = p.fr + 1;
    }
  }
}

int prebfs(int y, int x){
  if(!min_cost[y][x]) return 0;

  int ret = 1;
  fill_n( *used, 10000, false);
  queue< Pii > que;
  que.push(Pii( 0, Pi( y, x)));
  used[y][x] = true;


  while(!que.empty()){
    Pii p = que.front();
    que.pop();
    for(int i = 0 ; i < 6 ; i++ ){
      int ny = p.sc.fr + dy[i], nx = p.sc.sc + dx[p.sc.fr % 2][i];
      if(isover( ny, nx) || used[ny][nx] || min_cost[ny][nx] <= p.fr + 1) continue;
        que.push(Pii( p.fr + 1, Pi( ny, nx)));
        used[ny][nx] = true;
        ret++;
    }
  }
  return ret;
}

int main(){
  while(cin >> m, m){
    queue< Pii > que;
    fill_n( *min_cost, 10000, 1 << 30);

    cin >> n >> s;

    for(int i = 0 ; i < s ; i++ ){
      int x, y;
      cin >> x >> y;
      bfs( y - 1, x - 1);
    }

    int t, ret = 0;
    cin >> t;
    while(t--){
      int p, q;
      cin >> p >> q;
      ret = max( ret,prebfs( q - 1, p - 1));
    }
    cout << ret << endl;
  }
}