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){
  int res = (v[y][x] <= n ? 0 : 1);
  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);
  }
  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;
}

C++: //50
#include<iostream>
#include<algorithm>

using namespace std;

int main(){
  for(int m,n;cin>>m>>n,m;){
    int s;
    cin>>s;
    int g[100][100];
    fill(g[0],g[100],1<<29);
    int sh[100][100]={};
    for(int i=1;i<=s;i++){
      int x,y;
      cin>>x>>y;
      x--;
      y--;
      sh[y][x]=i;
      g[y][x]=0;
    }
    int a=0;
    int t;
    cin>>t;
    while(t--){
      int x,y;
      cin>>x>>y;
      x--;
      y--;
      int gg[100][100];
      copy(g[0],g[n],gg[0]);
      int ss[100][100];
      copy(sh[0],sh[n],ss[0]);
      ss[y][x]=-1;
      gg[y][x]=0;
      for(int i=0;i<m*n;i++){
	for(int j=0;j<n;j++){
	  for(int k=0;k<m;k++){
	    for(int l=0;l<6;l++){
	      int dy[]={-1,0,1,1,0,-1};
	      int dx[][6]={{0,1,0,-1,-1,-1},{1,1,1,0,-1,0}};
	      int ny=j+dy[l];
	      int nx=k+dx[j%2][l];
	      if(0<=min(nx,ny)&&ny<n&&nx<m){
		int c=gg[ny][nx]+1;
		if(c<gg[j][k]){
		  gg[j][k]=c;
		  ss[j][k]=ss[ny][nx];
		}else if(c==gg[j][k]){
		  if(ss[j][k]!=ss[ny][nx]){
		    ss[j][k]=0;
		  }
		}
	      }
	    }
	  }
	}
      }
      int c=0;
      for(int i=0;i<n;i++){
	for(int j=0;j<m;j++){
	  c+=ss[i][j]==-1;
	}
      }
      a=max(c,a);
    }
    cout<<a<<endl;
  }
  return 0;
}