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<stdio.h>
#include<algorithm>
#include<queue>
using namespace std;
int dx[2][6]={{-1,-1,0,0,1,1},{-1,-1,0,0,1,1}};
int dy[2][6]={{-1,0,-1,1,-1,0},{1,0,-1,1,1,0}};
int bfs[110][110];
int m[110][110];
int main(){
	int a,b;
	while(scanf("%d%d",&a,&b),a){
		int c;scanf("%d",&c);
		queue<pair<int,int> >Q;
		for(int i=0;i<a;i++)for(int j=0;j<b;j++)bfs[i][j]=-1;
		for(int i=0;i<c;i++){
			int p,q;scanf("%d%d",&q,&p);
			p--;q--;
			bfs[p][q]=0;
			Q.push(make_pair(p,q));
		}
		while(Q.size()){
			int row=Q.front().first;
			int col=Q.front().second;
			Q.pop();
			int t=row%2;
			for(int i=0;i<6;i++){
				if(0<=row+dx[t][i]&&row+dx[t][i]<a&&0<=col+dy[t][i]&&col+dy[t][i]<b&&!~bfs[row+dx[t][i]][col+dy[t][i]]){
					bfs[row+dx[t][i]][col+dy[t][i]]=bfs[row][col]+1;
					Q.push(make_pair(row+dx[t][i],col+dy[t][i]));
				}
			}
		}
		int ret=0;
		int d;scanf("%d",&d);
		for(int i=0;i<d;i++){
			int p,q;scanf("%d%d",&q,&p);p--;q--;
			for(int j=0;j<a;j++)for(int k=0;k<b;k++)m[j][k]=-1;
			m[p][q]=0;
			Q.push(make_pair(p,q));
			while(Q.size()){
				int row=Q.front().first;
				int col=Q.front().second;
				Q.pop();
				int t=row%2;
				for(int j=0;j<6;j++){
					if(0<=row+dx[t][j]&&row+dx[t][j]<a&&0<=col+dy[t][j]&&col+dy[t][j]<b&&!~m[row+dx[t][j]][col+dy[t][j]]){
						m[row+dx[t][j]][col+dy[t][j]]=m[row][col]+1;
						Q.push(make_pair(row+dx[t][j],col+dy[t][j]));
					}
				}
			}
			int val=0;
			for(int j=0;j<a;j++)for(int k=0;k<b;k++)if(bfs[j][k]>m[j][k])val++;
			ret=max(val,ret);
		}
		printf("%d\n",ret);
	}
}

C++: #include <iostream>
#include <vector>
#include <queue>
#include <utility>
#include <tuple>
using namespace std;
const int INF = 1e9;
// int dx[] = {1, 1, 0, -1, -1, 0};
// int dy[] = {0, 1, 1,  1,  0, -1};
int dx[] = {-1, 0, 1, -1, 0, 1};
int dy0[] = {0, -1, 0, 1, 1, 1};
int dy1[] = {-1, -1, -1, 0, 1, 0};
int main(){
  int m, n;
  while(cin >> m >> n, m){
    int s;
    cin >> s;
    vector<int> X(s), Y(s);
    queue<pair<size_t,size_t>> Q;
    vector<vector<int>> D(n,vector<int>(m,INF));
    for(int i = 0; i < s; ++i){
      size_t x, y;
      cin >> y >> x;
      --x,--y;
      Q.emplace(x,y);
      D[x][y] = 0;
    }
    while(Q.size()){
      size_t x, y;
      tie(x,y) = Q.front();
      Q.pop();
      int d = D[x][y];
      for(int i = 0; i < 6; ++i){
        int* dy = ((x % 2 == 0)? dy1:dy0);
        size_t x_ = x + dx[i], y_ = y + dy[i];
        if(x_ >= n or y_ >= m) continue;
        if(D[x_][y_] <= d+1) continue;
        D[x_][y_] = d+1;
        Q.emplace(x_,y_);
      }
    }
    // for(int i = 0; i < n; ++i)
    //   for(int j = 0; j < m; ++j)
    //     fprintf(stderr, "%d%c", D[i][j], j+1<m? ' ':'\n');
    int t;
    cin >> t;
    int ans = 0;
    for(int i = 0; i < t; ++i){
      size_t p, q;
      cin >> q >> p;
      --p,--q;
      // cerr << p << " " << q << "!!!" << endl;
      int ret = 0;
      queue<pair<size_t,size_t>> Q_;
      vector<vector<int>> D_ = D;
      if(D_[p][q] == 0) continue;
      D_[p][q] = 0;
      ++ret;
      Q_.emplace(p,q);
      while(Q_.size()){
        size_t x, y;
        tie(x,y) = Q_.front();
        Q_.pop();
        int d = D_[x][y];
        for(int j = 0; j < 6; ++j){
          int* dy = ((x % 2 == 0)? dy1:dy0);
          size_t x_ = x + dx[j], y_ = y + dy[j];
          if(x_ >= n or y_ >= m) continue;
          if(D_[x_][y_] <= d+1) continue;
          D_[x_][y_] = d+1;
          // cerr << x_ << " " << y_ << endl;
          ++ret;
          Q_.emplace(x_,y_);
        }
      }
      //cerr << p << " " << q << " " << ret << endl;
      ans = max(ans,ret);
    }
    cout << ans << endl;
  }
}