#include <vector>#include <algorithm>#include <unordered_set>#include <utility>using namespace std;struct pairhash {public:  template <typename T, typename U>  std::size_t operator()(const std::pair<T, U> &x) const  {    return std::hash<T>()(x.first) * 37 ^ std::hash<U>()(x.second);  }};class TheGridDivTwo {public:	unordered_set<pair<int, int>, pairhash> visited;	unordered_set<pair<int, int>, pairhash> block;	int find(vector <int> x, vector <int> y, int k) {		for (int i = 0; i < x.size(); i++) {			block.insert(make_pair(x[i], y[i]));		}		int result = 0;		pair<int, int> start = make_pair(0, 0);		findRe(result, start, k, 0);		return result;	}	void findRe(int &result, pair<int, int> &p, int k, int step) {		visited.insert(p);		if (step == k) {			result = max(result, p.first);		} else {			int dx[4] = {1, 0, 0, -1};			int dy[4] = {0, 1, -1, 0};			for (int i = 0; i < 4; i++) {				pair<int, int> tmp = make_pair(p.first + dx[i], p.second + dy[i]);				if (tmp.first + k - step > result && valid(tmp)) {					findRe(result, tmp, k, step + 1);				}			}		}		visited.erase(p);	}	bool valid(pair<int, int> &p) {		if (block.find(p) != block.end() || visited.find(p) != visited.end()) {			return false;		}		return true;	}};