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 <complex>
#include <sstream>
#include <string>
#include <algorithm>
#include <deque>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <vector>
#include <set>
#include <limits>
#include <cstdio>
#include <cctype>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <ctime>
using namespace std;
#define REP(i, j) for(int i = 0; i < (int)(j); ++i)
#define FOR(i, j, k) for(int i = (int)(j); i < (int)(k); ++i)
#define SORT(v) sort((v).begin(), (v).end())
#define REVERSE(v) reverse((v).begin(), (v).end())
typedef pair<int, int> P;
typedef pair<int, P> PP;

int mx[2][6] = {
  {-1, 0, 1, 0, -1, -1},
  {0, 1, 1, 1, 0, -1}
};
int my[2][6] = {
  {-1, -1, 0, 1, 1, 0},
  {-1, -1, 0, 1, 1, 0}
};

int W, H, S, T;

void update(int sy, int sx, vector< vector<int> > &v){
  queue<PP> open;
  open.push(PP(0, P(sy, sx)));
  v[sy][sx] = 0;
  while(!open.empty()){
    PP pp = open.front(); open.pop();
    int y = pp.second.first, x = pp.second.second, n = pp.first, t = (y % 2 == 0);
    REP(i, 6){
      int ny = y + my[t][i], nx = x + mx[t][i];
      if(ny <= 0 || nx <= 0 || ny > H || nx > W || v[ny][nx] <= n + 1) continue;
      v[ny][nx] = n + 1;
      open.push(PP(n + 1, P(ny, nx)));
    }
  }
}

int count(int sy, int sx, vector< vector<int> > &v){
  queue<PP> open;
  open.push(PP(0, P(sy, sx)));
  vector< vector<bool> > visited(H + 1, vector<bool>(W + 1, 0));
  visited[sy][sx] = 1;
  int res = 0;
  while(!open.empty()){
    PP pp = open.front(); open.pop();
    int y = pp.second.first, x = pp.second.second, n = pp.first, t = (y % 2 == 0);
    if(v[y][x] > n) ++res;
    REP(i, 6){
      int ny = y + my[t][i], nx = x + mx[t][i];
      if(ny <= 0 || nx <= 0 || ny > H || nx > W || v[ny][nx] <= n + 1 || visited[ny][nx]) continue;
      visited[y][x] = 1;
      open.push(PP(n + 1, P(ny, nx)));
    }
  }
  return res;
}

int main() {
  while(cin >>W >>H && W && H){
    vector< vector<int> > v(H + 1, vector<int>(W + 1, 1e9));
    cin >>S;
    REP(s, S){
      int x, y; cin >>x >>y;
      update(y, x, v);
    }
    cin >>T;
    int ans = 0;
    REP(t, T){
      int x, y; cin >>x >>y;
      ans = max(ans, count(y, x, v));
    }
    cout <<ans <<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <queue>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
typedef pair<pair<int,int>,int> NODE;
#define X first.second
#define Y first.first
#define depth second

/*ï*/
int ox[] = {-1, 1, 0, 0, 1,1};
int oy[] = { 0, 0,-1, 1,-1,1};

/*ô*/
int ex[] = {-1, 1, 0, 0,-1,-1};
int ey[] = { 0, 0,-1, 1,-1, 1};

int main(){
	int point[100][100];
	int h,w,a,b,t,x,y,s;
	while(cin >> w  && w){
		int ret = 0;
		cin >> h;
		rep(i,100)rep(j,100)point[i][j] = 0;
		cin >> t;
		rep(i,t){
			cin >> a >> b;
			a--;b--;
			point[b][a] = i+1;
		}
		cin >> s;
		rep(P,s){
			cin >> a >> b;
			a--;b--;
			point[b][a] = 50;
			
		//rep(i,h){rep(j,w)cout << point[i][j];cout << endl;}
		int pt[100] = {0};
		rep(i,h)rep(j,w){
			x = j,y = i;
			queue<NODE> Q;
			pair<int,int> dp[100];
			bool done[100][100]={0};
			Q.push( make_pair(make_pair(y,x),0	) );
			while( Q.size() ){
				NODE q = Q.front(); Q.pop();
				if(point[q.Y][q.X]){
					dp[q.depth].first++;
					dp[q.depth].second = point[q.Y][q.X];
			  }
				if( q.Y % 2 == 1){
					rep(L,6){
						if( q.X+ox[L] >=0 && q.X+ox[L] < w && q.Y+oy[L] < h && q.Y+oy[L]>=0 ){
								if( !done[q.Y+oy[L]][q.X+ox[L]] )Q.push( make_pair(make_pair(q.Y+oy[L],q.X+ox[L]),q.depth+1) );
							  	done[q.Y+oy[L]][q.X+ox[L]] = true;
						}
					}
				}else{
					rep(L,6){
						if( q.X+ex[L] >=0 && q.X+ex[L] < w && q.Y+ey[L] < h && q.Y+ey[L]>=0 ){
									if( !done[q.Y+ey[L]][q.X+ex[L]] )Q.push( make_pair(make_pair(q.Y+ey[L],q.X+ex[L]),q.depth+1) );
							  	done[q.Y+ey[L]][q.X+ex[L]] = true;
						}
					}
				}
			}
			rep(I,100){
				if(dp[I].first){
					if(dp[I].first==1)
						pt[dp[I].second-1]++;
					break;
				}
			}
		}
			ret = max(pt[49],ret);
			point[b][a] = 0;
		}
		cout << ret << endl;
	}
	
}