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 <cstring>
using namespace std;

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

#define REP(i,n,m) for(int i=n;i<m;i++)
#define rep(i,n) REP(i,0,n)
#define INF 999999999

int w,h,s,t;
int f[102][102]; //eXÌèÌóµ
int d[102][102]; //e}X©çêÔß¢XÖÌÅ¬£
bool closed[102][102]; //Dæp

int dx1[] = { 0, 1, 1, 1, 0,-1}; //ïñ©çÌJÚ
int dy1[] = {-1,-1, 0, 1, 1, 0}; //ïñ
int dx2[] = {-1, 0, 1, 0,-1,-1}; //ôñ
int dy2[] = {-1,-1, 0, 1, 1, 0}; //ôñ

//flg : }bvðhé©hçÈ¢©
int draw(int x,int y,int id,bool flg){
	int res = 0;
	queue<PP> q;
	memset(closed,0,sizeof(closed));

	q.push(PP(P(x,y),0));

	while(!q.empty()){
		PP p = q.front(); q.pop();
		int x = p.first.first;
		int y = p.first.second;
		if(closed[y][x]) continue;
		closed[y][x] = true;

		if(d[y][x] == p.second && flg){
			f[y][x] = INF;
		}
		else if(d[y][x] > p.second){
			if(flg){
				f[y][x] = id;
				d[y][x] = p.second;
			}
			res++;
		}

		for(int i=0;i<6;i++){
			int nx = x + (y%2==1 ? dx1[i] : dx2[i]);
			int ny = y + (y%2==1 ? dy1[i] : dy2[i]);
			if(nx>=0 && nx<w && ny>=0 && ny<h){
				q.push(PP(P(nx,ny),p.second+1));
			}
		}
	}
	return res;
}

int main(void){
	while(cin>>w>>h,w){
		rep(i,h) rep(j,w) f[i][j] = d[i][j] = INF;

		//àÆ©ç éXÌèÌóµð}bvÉ«Þ
		cin>>s;
		rep(i,s){
			int p,q;
			cin>>p>>q;
			draw(p-1,q-1,i,true);
		}

		//eóânÉu¢½Æ«ÌóµðÀÛÉV~[g
		int ans = 0;
		cin>>t;
		rep(i,t){
			int p,q;
			cin>>p>>q;
			ans = max(ans,draw(p-1,q-1,i,false));
		}

		cout<<ans<<endl;
	}

	return 0;
}

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

#define REP(i,n) for(int i=1; i<=n; i++)
#define ABS(n) (n<0?-n:n)

#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;
		REP(y,h)REP(x,w)
		{
			field[y][x] = INF;
		}
		
		cin >> n;
		while(n--)
		{
			cin >> x0 >> y0;
			REP(y,h)REP(x,w)
			{
				field[y][x] = min(field[y][x],dist(x0,y0,x,y));
			}
		}

		ans = 0;
		cin >> n;
		while(n--)
		{
			cnt = 0;
			cin >> x0 >> y0;
			REP(y,h)REP(x,w)
			{
				if(field[y][x]>dist(x0,y0,x,y)) cnt++;
			}
			ans = max(ans,cnt);
		}

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

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){
  int res = (v[y][x] <= n ? 0 : 1);
  visited[y][x] = 1;
  v[y][x] = n;
  int 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 || visited[ny][nx]) continue;
    res += count(ny, nx, n + 1, v, visited);
  }
  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));
    }
    cout <<res <<endl;
  }
  return 0;
}