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<vector>
#include<queue>
#include<tuple>
#include<set>
#include<algorithm>
using namespace std;

const int INF = 10000000;

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;
    }
}

C++: #define _USE_MATH_DEFINES
#include<cstdio>
#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<stack>
#include<cmath>
#include<climits>
using namespace std;

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

struct Data{
	int y, x;
	bool is_deven;
	Data(){}
	Data(int _y, int _x, bool _is_deven){
		y = _y; x = _x; is_deven = _is_deven;
	}
};

int main(){
	int N, M, S, T, X[10], Y[10], P, Q;
	while(cin >> N >> M, N || M){
		cin >> S;
		for(int i = 0; i < S; i++){
			cin >> X[i] >> Y[i];
			X[i]--; Y[i]--;
		}

		cin >> T;
		int ans = 0;
		for(int i = 0; i < T; i++){
			cin >> P >> Q;
			P--; Q--;

			queue<Data> q;
			Data q_front;
			bool used[100][100] = {};
			int deven_scope = 0;
			
			for(int j = 0; j < S; j++){
				q.push( Data(Y[j], X[j], false) );
			}
			q.push( Data(Q, P, true) );

			while( !q.empty() ){
				q_front = q.front(); q.pop();

				if(used[q_front.y][q_front.x]) continue;
				used[q_front.y][q_front.x] = true;

				if(q_front.is_deven) deven_scope++;
				
				for(int j = 0; j < 6; j++){
					int ny = q_front.y + dy[j];
					int nx = q_front.x + dx[q_front.y&1][j];
					
					if(ny < 0 || N <= ny || nx < 0 || M <= nx) continue;

					q.push( Data(ny, nx, q_front.is_deven) );
				}
			}
			ans = max(ans, deven_scope);
		}
		printf("%d\n", ans);
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

const int dx[7] = {0, 0, -1, -1, 0, 1, 1};
const int dy[2][7] = {
	{0, -1, -1, 0, 1, 0, -1},
	{0, -1, 0, 1, 1, 1, 0}
};

int n, m;
int g[100][100];
int grid[100][100];
int grid2[100][100];

bool ok(int i, int j)
{
	return i >= 0 && j >= 0 && i < n && j < m;
}

int solve()
{
	int maxi = 0;
	memcpy(grid, g, sizeof(g));
	for (int a = 0; a < 100; a++){
		memset(grid2, 0, sizeof(grid2));
		for (int i = 0; i < n; i++){
			for (int j = 0; j < m; j++){
				for (int dir = 0; dir < 7; dir++){
					int nx = i + dx[dir];
					int ny = j + dy[i % 2][dir];
					if (!ok(nx, ny)) continue;
					grid2[nx][ny] |= grid[i][j];
				}
			}
		}
		
		int cnt = 0;
		for (int i = 0; i < n; i++){
			for (int j = 0; j < m; j++){
				if (grid2[i][j] == (grid2[i][j] & (-grid2[i][j]))){
					grid[i][j] = grid2[i][j];
					if (grid[i][j] == 1) cnt++;
				}
				//printf("%d ", grid[i][j]);
			}
			//puts("");
		}
		maxi = max(maxi, cnt);
	}
	return maxi;
}

int main()
{
	while (scanf("%d %d", &m, &n), m){
		memset(g, 0, sizeof(g));
		int maxi = 0;
		int s;
		scanf("%d", &s);
		for (int i = 0; i < s; i++){
			int x, y;
			scanf("%d %d", &x, &y);
			g[--y][--x] = 1 << i + 1;
		}
		int t;
		scanf("%d", &t);
		for (int i = 0; i < t; i++){
			int p, q;
			scanf("%d %d", &p, &q);
			g[--q][--p] = 1;
			maxi = max(maxi, solve());
			g[q][p] = 0;
		}
		printf("%d\n", maxi);
	}
	
	return 0;
}