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<cstring>
#include<queue>

using namespace std;

typedef pair<int,int> P;

int fie[101][101];
int cox[11],coy[11];
int conx[11],cony[11];
int m,n,s,sn;
int ans=0;
const int dx1[6]={-1,-1,-1,0,1,0};
const int dx2[6]={0,-1,0,1,1,1};
const int dy[6]={-1,0,1,-1,0,1};
const int INF=100000;

void bfs(int x,int y){
	queue<P> que;
	que.push(P(x,y));
	fie[x][y]=0;
	while(que.size()){
		P p=que.front();que.pop();
		int kx=p.first,ky=p.second;
		for(int i=0;i<6;i++){
			int fx=kx,fy=ky+dy[i];
			if(ky%2==1)fx+=dx1[i];
			if(ky%2==0)fx+=dx2[i];
			if(fx>=1 && fx<=m && fy>=1 && fy<=n){
				if(fie[fx][fy]>fie[kx][ky]+1){
					que.push(P(fx,fy));
					fie[fx][fy]=fie[kx][ky]+1;
				}
			}
		}
	}
}

int bfs2(int x,int y,int fie2[101][101]){
	int res=1;
	queue<P> que;
	que.push(P(x,y));
	fie2[x][y]=0;
	while(que.size()){
		P p=que.front();que.pop();
		int kx=p.first,ky=p.second;
		for(int i=0;i<6;i++){
			int fx=kx,fy=ky+dy[i];
			if(ky%2==1)fx+=dx1[i];
			if(ky%2==0)fx+=dx2[i];
			if(fx>=1 && fx<=m && fy>=1 && fy<=n){
				if(fie2[fx][fy]>fie2[kx][ky]+1){
					que.push(P(fx,fy));
					fie2[fx][fy]=fie2[kx][ky]+1;
					res++;
				}
			}
		}
	}
	return res;
}

int main(void){
	while(1){
		scanf("%d",&m);
		if(m==0)break;
		scanf("%d",&n);
		for(int i=0;i<=100;i++){
			for(int j=0;j<=100;j++){
				fie[i][j]=INF;
			}
		}
		ans=0;
		scanf("%d",&s);
		for(int i=0;i<s;i++){
			scanf("%d%d",&cox[i],&coy[i]);
			bfs(cox[i],coy[i]);
		}
		scanf("%d",&sn);
		for(int i=0;i<sn;i++){
			scanf("%d%d",&conx[i],&cony[i]);
			ans=max(ans,bfs2(conx[i],cony[i],fie));
		}
		printf("%d\n",ans);
	}
    return 0;
}

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

const int INF = 100000;

class Node {
public:
    int y, x, depth;
    Node(int y, int x, int d) :y(y), x(x), depth(d) {}
};

typedef tuple<int, int> Point;

enum {EVEN, ODD};
enum {Y, X};
const int NEXT[2][6][2] = {
    {
        {0, -1},
        {-1, -1},
        {-1, 0},
        {0, 1},
        {1, -1},
        {1, 0},
    },
    {
        {0, -1},
        {-1, 0},
        {-1, 1},
        {0, 1},
        {1, 0},
        {1, 1},
    },
};

int bfs(vector<vector<int>>& hex, int y, int x, bool write) {
    int h = hex.size(), w = hex[0].size();
    int result = 0;
    set<Point> visited;
    queue<Node> q;
    q.push(Node(y, x, 0));
    while(!q.empty()) {
        Node current = q.front();
        q.pop();
        if(visited.count(Point(current.y, current.x))) continue;
        visited.insert(Point(current.y, current.x));
        if(hex[current.y][current.x] <= current.depth) continue;
        if(write) hex[current.y][current.x] = current.depth;
        ++result;
        for(const auto& d: NEXT[y & 1]) {
            int ny = current.y + d[Y];
            int nx = current.x + d[X];
            if(ny < 0 || h <= ny) continue;
            if(nx < 0 || w <= nx) continue;
            q.push(Node(ny, nx, current.depth + 1));
        }
    }
    return result;
}

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