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 = 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;
    queue<Node> q;
    q.push(Node(y, x, 0));
    while(!q.empty()) {
        Node current = q.front();
        q.pop();
        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++: #include <iostream>
#include <vector>
#include <queue>
using namespace std;

int H, W, N, M, p[100], q[100], x, y, dist[109][109][11]; vector<pair<int, int>> X[109][109];
int dy1[6] = { 0,0,-1,-1,1,1 }, dx1[6] = { -1,1,-1,0,-1,0 };
int dy2[6] = { 0,0,-1,-1,1,1 }, dx2[6] = { -1,1,0,1,0,1 };

int solve() {
	for (int i = 1; i <= H; i++) { for (int j = 1; j <= W; j++) { for (int k = 0; k <= N; k++) dist[i][j][k] = (1 << 30); } }
	for (int i = 0; i <= N; i++) {
		queue<pair<int, int>>Q;
		Q.push(make_pair(p[i], q[i])); dist[p[i]][q[i]][i] = 0;
		while (!Q.empty()) {
			int to1 = Q.front().first, to2 = Q.front().second; Q.pop();
			for (int j = 0; j < X[to1][to2].size(); j++) {
				int p1 = X[to1][to2][j].first, p2 = X[to1][to2][j].second;
				if (dist[p1][p2][i] > dist[to1][to2][i] + 1) {
					dist[p1][p2][i] = dist[to1][to2][i] + 1;
					Q.push(make_pair(p1, p2));
				}
			}
		}
	}
	int ans = 0;
	for (int i = 1; i <= H; i++) {
		for (int j = 1; j <= W; j++) {
			bool OK = true;
			for (int k = 1; k <= N; k++) {
				if (dist[i][j][0] >= dist[i][j][k]) OK = false;
			}
			if (OK == true) ans++;
		}
	}
	return ans;
}

int main() {
	while (true) {
		cin >> H >> W; if (H == 0) break;
		for (int i = 0; i < 109; i++) { for (int j = 0; j < 109; j++) X[i][j].clear(); }
		for (int i = 1; i <= H; i++) {
			for (int j = 1; j <= W; j++) {
				for (int k = 0; k < 6; k++) {
					int fx = i, fy = j;
					if (j % 2 == 1) { fx += dx1[k]; fy += dy1[k]; }
					if (j % 2 == 0) { fx += dx2[k]; fy += dy2[k]; }
					if (fx <= 0 || fy <= 0 || fx > H || fy > W) continue;
					X[i][j].push_back(make_pair(fx, fy));
				}
			}
		}
		cin >> N;
		for (int i = 1; i <= N; i++) { cin >> p[i] >> q[i]; }
		int ret = 0;
		cin >> M;
		for (int i = 1; i <= M; i++) {
			cin >> x >> y;
			p[0] = x; q[0] = y;
			ret = max(ret, solve());
		}
		cout << ret << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <cmath>
using namespace std;

#define ABS(n) (n<0?-(n):(n))

#define INF (1<<20)
int field[128][128];

int dist(int x1, int y1, int x2, int y2)
{
	x1-=(y1-1)/2;
	x2-=(y2-1)/2;

	return (ABS(x1-x2)+ABS(y1-y2)+ABS((x1+y1)-(x2+y2)))/2;
}

int main()
{
	int w,h,n,x0,y0,cnt,ans;
	while(cin >> w, w)
	{
		cin >> h;
		for(int y=1; y<=h; y++)
		for(int x=1; x<=w; x++)
		{
			field[y][x] = INF;
		}
		
		cin >> n;
		while(n--)
		{
			cin >> x0 >> y0;
			for(int y=1; y<=h; y++)
			for(int x=1; x<=w; x++)
			{
				field[y][x] = min(field[y][x],dist(x0,y0,x,y));
			}
		}

		ans = 0;
		cin >> n;
		while(n--)
		{
			cnt = 0;
			cin >> x0 >> y0;
			for(int y=1; y<=h; y++)
			for(int x=1; x<=w; x++)
			{
				if(field[y][x]>dist(x0,y0,x,y)) cnt++;
			}
			ans = max(ans,cnt);
		}
		cout << ans << endl;
	}
	return 0;
}