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>
#define mp make_pair
using namespace std;
typedef pair<int, int> pii;//x, y
typedef pair<int, pii> piii;//cost, x, y
int dx[6] = {1, 1, 1, 0, -1, 0},
  dy[6] = {-1, 0, 1, 1, 0, -1};
int grid[110][110];
int n, m, a;

int bfs(int grid[110][110], int sx, int sy){
  queue<piii> que;
  int ans = 0;
  grid[sy][sx] = 0;
  que.push(mp(0, mp(sx, sy)));
  while(!que.empty()){
    piii p = que.front();que.pop();
    int cost = p.first;
    int x    = p.second.first;
    int y    = p.second.second;
    for (int i = 0; i < 6; i++) {
      int nx = x + dx[i], ny = y + dy[i];
      if(0 <= ny && ny < n &&
         0 <= nx && nx < m &&
         grid[ny][nx] > cost + 1){
        ans++;
        grid[ny][nx] = cost + 1;
        que.push(mp(cost + 1, mp(nx, ny)));
      }
    }
  }
  // for (int i = 0; i < n; i++) {
  //   for (int j = 0; j < m; j++) {
  //     std::cout << grid[i][j] << " ";
  //   }
  //   std::cout << std::endl;
  // }
  // std::cout << std::endl;

  return ans;
}

int main(int argc, char *argv[]){
  while(cin >> m >> n, n){
    int ans = 0, t;
    cin >> a;
    int sx[a], sy[a];
    for (int i = 0; i < a; i++) {
      cin >> sx[i] >> sy[i];
      sx[i]--;sy[i]--;
    }
    cin >> t;
    int px[t], py[t];
    for (int i = 0; i < t; i++) {
      cin >> px[i] >> py[i];
      px[i]--;py[i]--;
    }
    
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        grid[i][j] = 1e8;
      }
    }
    
    for (int i = 0; i < a; i++) {
      bfs(grid, sx[i], sy[i]);
    }

    for (int i = 0; i < t; i++) {
      int tmp[110][110];
      
      for (int j = 0; j < n; j++) {
        for (int k = 0; k < m; k++) {
          tmp[j][k] = grid[j][k];
        }
      }
      
      ans = max(ans, bfs(tmp, px[i], py[i]));
    }
    std::cout << ans << std::endl;
  }
  return 0;
}

C++: #include<iostream>
#include<vector>
#include<queue>
using namespace std;
typedef vector<int> vi;
typedef vector<vi> grid;

const int INF = 1e9;
const int dx[6] = {0,1,1,1,0,-1}, dy[6] = {-1,-1,0,1,1,0};
int h,w;

grid bfs(int y, int x){
  grid res(h,vi(w,INF));
  res[y][x] = 0;
  queue<int> q;
  q.push(y*w+x);
  
  while(q.size()){
    y = q.front()/w; x = q.front()%w; q.pop();
    int c = res[y][x];

    for(int i=0;i<6;i++){
      int ny = y+dy[i], nx = x+dx[i] + ((y%2==0 && i%3!=2)?-1:0);
      if(ny<0 || nx<0 || ny>=h || nx>=w)continue;
      if(res[ny][nx]>c+1){
	res[ny][nx] = c+1;
	q.push(ny*w+nx);
      }
    }
  }
  return res;
}

int main(){
  while(cin >> h >> w, h){
    grid g(h,vi(w,INF));

    int s;
    cin >> s;
    for(int z=0;z<s;z++){
      int a,b; cin >> a >> b; a--; b--;
      grid tmp = bfs(b,a);

      for(int i=0;i<h;i++){
	for(int j=0;j<w;j++)g[i][j] = min(g[i][j], tmp[i][j]);
      }
    }

    int t, res = 0;
    cin >> t;
    for(int z=0;z<t;z++){
      int a,b; cin >> a >> b; a--; b--;
      grid tmp = bfs(b,a);
      int cover = 0;
      for(int i=0;i<h;i++){
	for(int j=0;j<w;j++){
	  if(g[i][j] > tmp[i][j])cover++;
	}
      }
      res = max(res, cover);
    }
    
    cout << res << endl;
  }
}

C++: #include<iostream>
#include<vector>
#include<queue>
#include<tuple>
#include<climits>
#include<algorithm>
using namespace std;

enum{X, Y, DEPTH};
typedef tuple<int, int, int> Node;

int dx[2][6] = {{-1, 0, -1, 1, -1, 0}, {0, 1, -1, 1, 0, 1}};
int dy[2][6] = {{-1, -1, 0, 0, 1, 1}, {-1, -1, 0, 0, 1, 1}};

int m, n;
vector<vector<int>> field;

int bfs(int start_x, int start_y, bool write) {
    int result = 0;
    vector<vector<int>> visited(m, vector<int>(n, 0));
    queue<Node> q;
    q.push(Node(start_x, start_y, 0));
    while(!q.empty()) {
        int x = get<X>(q.front());
        int y = get<Y>(q.front());
        int depth = get<DEPTH>(q.front());
        q.pop();
        if(visited[x][y]) continue;
        visited[x][y] = 1;
        if(field[x][y] <= depth) continue;
        if(write) field[x][y] = depth;
        ++result;
        for(int i = 0; i < 6; ++i) {
            int nx = x + dx[y & 1][i];
            int ny = y + dy[y & 1][i];
            if(nx < 0 || m <= nx || ny < 0 || n <= ny) continue;
            q.push(Node(nx, ny, depth + 1));
        }
    }
    return result;
}

int main() {
    int s, t;
    int x, y;
    while(cin >> m >> n, m | n) {
        field = vector<vector<int>>(m, vector<int>(n, INT_MAX));
        for(cin >> s; s > 0; --s) {
            cin >> x >> y;
            bfs(x - 1, y - 1, true);
        }
        int answer = 0;
        for(cin >> t; t > 0; --t) {
            cin >> x >> y;
            answer = max(answer, bfs(x - 1, y - 1, false));
        }
        cout << answer << endl;
    }
}