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<queue>
#include<algorithm>
#include<vector>
#include<map>
using namespace std;
typedef pair < int , int > Pi;
typedef pair < int , Pi > Pii;
#define fr first
#define sc second

int m, n, s;
int min_cost[100][100];
int dy[] = { -1, -1, 0, 1, 1, 0};
int dx[][6] = {{ -1, 0, 1, 0, -1, -1}, { 0, 1, 1, 1, 0, -1}};

bool isover(int y, int x){
  return y < 0 || y >= n || x < 0 || x >= m;
}

void bfs(int y, int x){
  queue< Pii > que;
  que.push(Pii( 0, Pi( y, x)));
  min_cost[y][x] = 0;
  while(!que.empty()){
    Pii p = que.front();
    que.pop();
    for(int i = 0 ; i < 6 ; i++ ){
      int ny = p.sc.fr + dy[i], nx = p.sc.sc + dx[p.sc.fr % 2][i];
      if(isover( ny, nx) || min_cost[ny][nx] < p.fr + 1) continue;
      que.push(Pii( p.fr + 1, Pi( ny, nx)));
      min_cost[ny][nx] = p.fr + 1;
    }
  }
}

int prebfs(int y, int x){
  int ret = 0;
  bool used[100][100] = {{}};
  queue< Pii > que;
  que.push(Pii( 0, Pi( y, x)));

  if(!min_cost[y][x]) return 0;

  while(!que.empty()){
    Pii p = que.front();
    que.pop();
    if(used[p.sc.fr][p.sc.sc]++) continue;
    ret++;
    for(int i = 0 ; i < 6 ; i++ ){
      int ny = p.sc.fr + dy[i], nx = p.sc.sc + dx[p.sc.fr % 2][i];
      if(isover( ny, nx) || min_cost[ny][nx] <= p.fr + 1) continue;

      que.push(Pii( p.fr + 1, Pi( ny, nx)));
    }
  }
  return ret;
}

int main(){
  while(cin >> m, m){
    queue< Pii > que;
    fill_n( *min_cost, 10000, 1 << 30);

    cin >> n >> s;

    for(int i = 0 ; i < s ; i++ ){
      int x, y;
      cin >> x >> y;
      bfs( y - 1, x - 1);
    }

    int t, ret = 0;
    cin >> t;
    while(t--){
      int p, q;
      cin >> p >> q;
      ret = max( ret,prebfs( q - 1, p - 1));
    }
    cout << ret << endl;
  }
}

C++: #include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = unsigned;
using u64 = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max()/32*15+208;

int main() {
    int dys[] = {-1, -1, 0, 0, 1, 1};
    int dx_odd[] = {-1, 0, -1, 1, -1, 0};
    int dx_even[] = {0, 1, -1, 1, 0, 1};
    int n, m;
    while(cin >> m >> n, m){
        vector<vector<int>> v(n+2, vector<int>(m+2, -1));
        auto ddist = v;
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < m; ++j) {
                v[i+1][j+1] = 0;
                ddist[i+1][j+1] = INF<int>;
            }
        }
        int s;
        cin >> s;
        vector<int> ys(s), xs(s);
        for (int i = 0; i < s; ++i) {
            cin >> xs[i] >> ys[i];
        }
        int ans = 0;
        int q;
        cin >> q;
        for (int i = 0; i < q; ++i) {
            int xx, yy;
            cin >> xx >> yy;
            ys.emplace_back(yy);
            xs.emplace_back(xx);
            auto vv = v, dist = ddist;
            queue<pair<int, int>> Q;
            for (int j = 0; j < ys.size(); ++j) {
                Q.emplace(ys[j], xs[j]);
                vv[ys[j]][xs[j]] = j+1;
                dist[ys[j]][xs[j]] = 0;
            }
            while(!Q.empty()){
                int y, x; tie(y, x) = Q.front(); Q.pop();
                for (int k = 0; k < 6; ++k) {
                    int ya = y + dys[k], xa = x + (y&1 ? dx_odd :dx_even)[k];
                    if(!~v[ya][xa]) continue;
                    if(dist[ya][xa] > dist[y][x]+1){
                        dist[ya][xa] = dist[y][x]+1;
                        vv[ya][xa] = vv[y][x];
                        Q.emplace(ya, xa);
                    }else if(dist[ya][xa] == dist[y][x]+1) {
                        if(vv[ya][xa] != vv[y][x]){
                            vv[ya][xa] = -1;
                        }
                    }
                }
            }
            int val = 0;
            for (int j = 0; j < n; ++j) {
                for (int k = 0; k < m; ++k) {
                    val += (vv[j+1][k+1] == ys.size());
                    // cout << vv[j+1][k+1] << " ";
                }
                // puts("");
            }
            ans = max(ans, val);
            ys.pop_back();
            xs.pop_back();
        }
        cout << ans << "\n";
    }
    return 0;
}