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>
#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[] = {-1,0,1,-1,0,1};
int dx[][6] = {{ -1,-1,-1,0,1,0}, {0,-1,0,1,1,1}};

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

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){
    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;
  }
}

C++: #include <iostream>
#include <fstream>
#include <sstream>
#include <iomanip> 
#include <complex> 
#include <string>
#include <vector> 
#include <list>
#include <deque> 
#include <stack> 
#include <queue> 
#include <set>
#include <map>
#include <bitset>
#include <functional>
#include <utility>
#include <algorithm> 
#include <numeric> 
#include <typeinfo> 
#include <cstdio>
#include <cstdlib> 
#include <cstring>
#include <cmath>
#include <climits> 
#include <ctime>
using namespace std;

int m,n;
int s,t;
typedef pair<int,int> P;
typedef pair<P,int> PP;
const int INF=10000000;
int field[101][101];
int x[11],y[11];
int nx[11],ny[11];
int dx1[6]={0,-1,0,1,1,1};
int dx2[6]={-1,-1,-1,0,1,0};
int dy[6]={-1,0,1,-1,0,1};

void bfs(int sx,int sy){
	queue<PP> que;
	que.push(PP(P(sx,sy),0));
	field[sx][sy]=0;
	while(que.size()){
		PP q=que.front();que.pop();
		int cx=q.first.first,cy=q.first.second;
		int c=q.second;
		for(int i=0;i<6;i++){
			int py=cy+dy[i];
			int px=cx;
			if(cy%2==0)px+=dx1[i];
			if(cy%2==1)px+=dx2[i];
			if(px>=1 && px<=m && py>=1 && py<=n && field[px][py]>c+1){
				field[px][py]=c+1;
				que.push(PP(P(px,py),c+1));
			}
		}
	}
}

int bfs2(int sx,int sy,int field2[101][101]){
	queue<PP> que;
	int res=1;
	if(field2[sx][sy]==0)return 0;
	que.push(PP(P(sx,sy),0));
	while(que.size()){
		PP q=que.front();que.pop();
		int cx=q.first.first,cy=q.first.second;
		int c=q.second;
		for(int i=0;i<6;i++){
			int py=cy+dy[i];
			int px=cx;
			if(cy%2==0)px+=dx1[i];
			if(cy%2==1)px+=dx2[i];
			if(px>=1 && px<=m && py>=1 && py<=n && field2[px][py]>c+1){
				res++;
				que.push(PP(P(px,py),c+1));
			}
		}
	}
	return res;
}

int main(void){
	while(1){
		int ans=0;
		for(int i=0;i<=100;i++){
			for(int j=0;j<=100;j++){
				field[i][j]=INF;
			}
		}
		cin >> m;
		if(m==0)break;
		cin >> n;
		cin >> s;
		for(int i=0;i<s;i++){
			cin >> x[i] >> y[i];
			bfs(x[i],y[i]);
		}
		cin >> t;
		for(int i=0;i<t;i++){
			cin >> nx[i] >> ny[i];
			ans=max(ans,bfs2(nx[i],ny[i],field));
		}
		cout << ans << endl;
	}
    return 0;
}