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<cstdio>
#include<algorithm>
#include<queue>

using namespace std;
const int dx[2][6]={{1,-1,-1,0,-1,0},{1,-1,1,0,0,1}};
const int dy[2][6]={{0,0,1,1,-1,-1},{0,0,1,1,-1,-1}};
class P{
        public:
        int x;
        int y;
        int cost;
        int index;
        P(){}
        P(int x,int y,int cost,int index):x(x),y(y),cost(cost),index(index){}
};

class Data{
        public:
        int cost;
        int index;
        Data(){}
        Data(int cost,int index):cost(cost),index(index){}
};

int main(){
        int m,n;
        while(scanf("%d",&m),m){

                scanf("%d",&n);
                int s;
                scanf("%d",&s);

                queue< P > Q;
                int sx[100];
                int sy[100];
                for(int i = 0; i < s; i++){
                        scanf("%d%d",&sx[i],&sy[i]);
                }

                int t;
                scanf("%d",&t);
                int ans = -11000;
                for(int q = 0; q < t; q++){
                        int x,y;
                        Data vis[128][128];
                        queue< P > Q;
                        for(int i = 0; i < s; i++){
                                Q.push(P(sx[i],sy[i],1,i));
                        }
                        for(int i = 0; i < 120; i++){
                                for(int j = 0; j < 120; j++){
                                        vis[i][j] = Data(0,0);
                                }
                        }

                        scanf("%d%d",&x,&y);
                        Q.push(P(x,y,1,s));
                        while( Q.size() ){
                                P p = Q.front();Q.pop();
                                for(int i = 0; i < 6; i++){
                                        if(p.x+dx[p.y%2][i] < 0 || p.x+dx[p.y%2][i] > m || p.y+dy[p.y%2][i] < 0 || p.y+dy[p.y%2][i] > n)continue;
                                        if(vis[p.x+dx[p.y%2][i]][p.y+dy[p.y%2][i]].cost == p.cost+1){
                                                vis[p.x+dx[p.y%2][i]][p.y+dy[p.y%2][i]].cost = -1;
                                                continue;
                                        }
                                        if(vis[p.x+dx[p.y%2][i]][p.y+dy[p.y%2][i]].cost != 0)continue;
                                        Q.push(P(p.x+dx[p.y%2][i],p.y+dy[p.y%2][i],p.cost+1,p.index));
                                        vis[p.x+dx[p.y%2][i]][p.y+dy[p.y%2][i]] = Data(p.cost+1,p.index);
                                }

                        }
                        int res = 0;
                        for(int i = 0; i < 120; i++){
                                for(int j = 0; j < 120; j++){
                                        if(vis[i][j].index == s && vis[i][j].cost != -1)res++;
                                }
                        }
                        ans = max(ans,res);
                }
                printf("%d\n",ans-1);
        }
        return 0;
}

C++: #include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
using namespace std;

struct st { int x, y, c; };
int d[100][100], b[100][100], x[10], y[10];
int dx[][6]{ { 0,-1,0,1,1,1, },{-1,-1,-1,0,1,0} };
int dy[]{ -1,0,1,1,0,-1 };
int main() {
	int m, n, s;
	while (scanf("%d%d", &m, &n), m) {
		scanf("%d", &s);
		rep(i, s)scanf("%d%d", &x[i], &y[i]), x[i]--, y[i]--;
		int t; scanf("%d", &t);
		int Max = 0;
		rep(i, t) {
			int p, q; scanf("%d%d", &p, &q); p--; q--;
			queue<st>que;
			memset(d, -1, sizeof(d));
			rep(j, s) {
				d[x[j]][y[j]] = 0; b[x[j]][y[j]] = j;
				que.push({ x[j],y[j],j });
			}
			d[p][q] = 0; b[p][q] = s; que.push({ p,q,s });
			while (!que.empty()) {
				st p = que.front(); que.pop();
				rep(j, 6) {
					int nx = p.x + dx[!(p.y & 1)][j], ny = p.y + dy[j];
					if (0 <= nx&&nx < m && 0 <= ny&&ny < n) {
						if (d[nx][ny] == -1) {
							d[nx][ny] = d[p.x][p.y] + 1;
							b[nx][ny] = p.c;
							que.push({ nx,ny,p.c });
						}
						else if (d[nx][ny] == d[p.x][p.y] + 1)
							b[nx][ny] = -1;
					}
				}
			}
			int cnt = 0;
			rep(i, m)rep(j, n) {
				if (b[i][j] == s)cnt++;
			}
			Max = max(Max, cnt);
		}
		printf("%d\n", Max);
	}
}