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<vector>
#include<queue>
#include<string>
#include<iostream>
#include<cmath>
#include<map>
#include<set>
#include<climits>
using namespace std;
typedef vector<string>vs;
typedef vector<int>vi;
typedef vector<vi>vvi;
typedef vector<double>vd;
typedef pair<int,int>pii;
typedef long long ll;
typedef pair<ll,ll>pll;
typedef vector<ll>vl;
typedef pair<int,pii>piii;
#define rrep(i,x,n) for(int i=(x);i<(n);++i)
#define rep(i,x) rrep(i,0,(x))
#define fi first
#define se second
#define each(i,c) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();++i)
#define all(c) (c).begin(),(c).end()
#define rall(c) (c).rbegin(),(c).rend()
#define pb push_back
#define maxs(a,b) (a)=max(a,b)
#define mins(a,b) (a)=min(a,b)
///#include<sstream>
///#include<cstring>
///#include<stack>
///#include<complex>

const int dy[6]={-1,-1,0,0,1,1};
const int dx[][6]={{-1,0,-1,1,-1,0},{0,1,-1,1,0,1}};
const int INF=1e9;
int W,H;
int s,t;
int x[10],y[10];
int p[10],q[10];
int nearest[10000];
vector<int>G[10000];
void getNearest(){
    fill_n(nearest,H*W,INF);
    queue<int>Q;
    rep(i,s){
        Q.push(y[i]*W+x[i]);
        nearest[y[i]*W+x[i]]=0;
    }

    while(!Q.empty()){
        int pos=Q.front();Q.pop();
        rep(i,G[pos].size()){
            int to=G[pos][i];
            if(nearest[to]!=INF)continue;
            nearest[to]=nearest[pos]+1;
            Q.push(to);
        }
    }
}


int solve(int start){
    int dist[10000];
    queue<int>Q;
    Q.push(q[start]*W+p[start]);
    fill_n(dist,H*W,INF);
    dist[q[start]*W+p[start]]=0;
    int ret=0;
    while(!Q.empty()){
        int pos=Q.front();Q.pop();
        rep(i,G[pos].size()){
            int to=G[pos][i];
            if(dist[to]!=INF)continue;
            dist[to]=dist[pos]+1;
            Q.push(to);
        }
    }

    rep(i,H*W)if(nearest[i]>dist[i])ret++;


    return ret;
}
int main(){
    while(scanf("%d%d",&W,&H),W||H){
        scanf("%d",&s);
        rep(i,s){
            scanf("%d%d",&x[i],&y[i]);
            x[i]--;y[i]--;
        }
        scanf("%d",&t);
        rep(i,t){
            scanf("%d%d",&p[i],&q[i]);
            p[i]--;q[i]--;
        }
        rep(i,10000)G[i].clear();

        rep(i,H)rep(j,W){
            rep(k,6){
                int ty=i+dy[k],tx=j+dx[i&1][k];
                if(ty<0||ty>=H||tx<0||tx>=W)continue;
                G[i*W+j].pb(ty*W+tx);
            }
        }
        getNearest();

        int ma=0;

        rep(i,t)ma=max(ma,solve(i));

        printf("%d\n",ma);
    }
    return 0;
}

C++: #include<cstdio>
#include<cstring>
#include<utility>
#include<algorithm>
#include<queue>
using namespace std;
typedef struct pos
{
	int x,y,cost;
	bool operator ()(pos const& a, pos const& b) const
	{
		return a.cost>b.cost;
	}

}pos;

int M,N,S,T,m[101][101],i,j,p,q,R,t;

int bfs(int x,int y,int abj)
{
	int i,c=1,mx[2][6]={{-1,0,1,0,-1,-1},{0,1,1,1,0,-1}},
			  my[2][6]={{-1,-1,0,1,1,0},{-1,-1,0,1,1,0}};
	priority_queue<pos,vector<pos>,pos>Q;
	m[y][x]=0;
	pos tmp={x,y,0};
	Q.push(tmp);
	while(!Q.empty())
	{
		tmp=Q.top();Q.pop();
		for(i=0;i<abj;i++)
		{
			if(0<=tmp.y+my[tmp.y%2][i]&&tmp.y+my[tmp.y%2][i]<M&&0<=tmp.x+mx[tmp.y%2][i]&&tmp.x+mx[tmp.y%2][i]<N)
				if(m[tmp.y+my[tmp.y%2][i]][tmp.x+mx[tmp.y%2][i]]>tmp.cost+1)
				{
					m[tmp.y+my[tmp.y%2][i]][tmp.x+mx[tmp.y%2][i]]=tmp.cost+1;
					pos tmp2={tmp.x+mx[tmp.y%2][i],tmp.y+my[tmp.y%2][i],tmp.cost+1};
					c++;
					Q.push(tmp2);
				}
		}
	}
	return c;
}

int main()
{
	for(i=0;i<100;i++)
		for(j=0;j<100;j++)
		{

		}
	for(;~scanf("%d%d%d",&M,&N,&S),M;)
	{
		memset(m,0x7,sizeof(m));
		for(i=0;i<S;i++)
		{
			scanf("%d%d",&p,&q);
			bfs(p-1,q-1,6);
		}
		for(R=0,scanf("%d",&T),j=0;j<T;j++)
		{
			scanf("%d%d",&p,&q);
			t=bfs(p-1,q-1,6);
			R=t<R?R:t;
		}
		printf("%d\n",R);
	}
	return 0;
}