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 <sstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <cfloat>
using namespace std;

int hexDist(int y1, int x1, int y2, int x2)
{
    if(y1 > y2){
        swap(y1, y2);
        swap(x1, x2);
    }

    int x3 = x1 - (y2 - y1) / 2;
    int x4 = x1 + (y2 - y1) / 2;
    if((y2 - y1) % 2 == 1){
        if(y1 % 2 == 0)
            -- x3;
        else
            ++ x4;
    }

    if(x2 < x3)
        return (y2 - y1) + (x3 - x2);
    if(x2 > x4)
        return (y2 - y1) + (x2 - x4);
    return y2 - y1;
}

int main()
{
    for(;;){
        int m, n, s;
        cin >> m >> n >> s;
        if(m == 0)
            return 0;

        vector<vector<int> > dist(n, vector<int>(m, INT_MAX));
        for(int i=0; i<s; ++i){
            int x, y;
            cin >> x >> y;

            for(int j=0; j<n; ++j){
                for(int k=0; k<m; ++k){
                    dist[j][k] = min(dist[j][k], hexDist(j, k, y-1, x-1));
                }
            }
        }

        int t;
        cin >> t;

        int ret = 0;
        for(int i=0; i<t; ++i){
            int x, y;
            cin >> x >> y;

            int num = 0;
            for(int j=0; j<n; ++j){
                for(int k=0; k<m; ++k){
                    if(hexDist(j, k, y-1, x-1) < dist[j][k])
                        ++ num;
                }
            }
            ret = max(ret, num);
        }

        cout << ret << endl;
    }
}

C++: #include<queue>
#include<algorithm>
#include<iostream>
#include<string>
#include<cstdlib>
#include<cstring>
#include<cmath>
using namespace std;
int main(){
  int i,j,k;
  int w,h;
  while(cin>>w&&w){
    int n;
    cin>>h>>n;
    int sx[20],sy[20];
    for(i=0;i<n;i++){
      cin>>sx[i]>>sy[i];
      sx[i]--;
      sy[i]--;
    }
    int m;
    cin>>m;
    for(;i<n+m;i++){
      cin>>sx[i]>>sy[i];
      sx[i]--;
      sy[i]--;
    }
    unsigned a[100][100][20];
    memset(a,-1,sizeof(a));
    for(i=0;i<n+m;i++){
      queue<pair<pair<int,int>,int> > b;
      b.push(make_pair(make_pair(sx[i],sy[i]),0));
      while(b.empty()==0){
	int x,y,z;
	x=b.front().first.first;
	y=b.front().first.second;
	z=b.front().second;
	b.pop();
	if(0<=x&&x<w&&0<=y&&y<h&&a[x][y][i]>(unsigned)z){
	  a[x][y][i]=z;
	  b.push(make_pair(make_pair(x-1,y),z+1));
	  b.push(make_pair(make_pair(x+1,y),z+1));
	  if(y%2){
	    b.push(make_pair(make_pair(x+1,y+1),z+1));
	    b.push(make_pair(make_pair(x,y+1),z+1));
	    b.push(make_pair(make_pair(x+1,y-1),z+1));
	    b.push(make_pair(make_pair(x,y-1),z+1));
	  }else{
	    b.push(make_pair(make_pair(x-1,y+1),z+1));
	    b.push(make_pair(make_pair(x,y+1),z+1));
	    b.push(make_pair(make_pair(x-1,y-1),z+1));
	    b.push(make_pair(make_pair(x,y-1),z+1));
	  }
	}
      }
    }
    unsigned c[100][100];
    memset(c,-1,sizeof(c));
    for(i=0;i<h;i++){
      for(j=0;j<w;j++){
	for(k=0;k<n;k++)
	  c[j][i]=min(c[j][i],a[j][i][k]);
      }
    }
    int mx=0;
    for(i=n;i<n+m;i++){
      int ct=0;
      for(j=0;j<h;j++){
	for(k=0;k<w;k++){
	  if(a[k][j][i]<c[k][j])
	    ct++;
	}
      }
      mx=max(mx,ct);
    }
    cout<<mx<<endl;
  }
  return 0;
}