// includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define vrep(v, i) for(int i = 0; i < (v).size(); i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
#define dump(a, n) for(int i = 0; i < n; i++)cout << a[i] << "\n "[i + 1 != n];
#define dump2(a, n, m) for(int i = 0; i < n; i++)for(int j = 0; j < m; j++)cout << a[i][j] << "\n "[j + 1 != m];
#define bit(n) (1LL<<(n))
#define INT(n) int n; cin >> n;
#define LL(n) ll n; cin >> n;
#define DOUBLE(n) double n; cin >> n;
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
typedef complex<double> cd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}

ll power3(int i){
  ll res = 1;
  rep(j, i)res *= 3;
  return res;
}

int idx = 0;
vector<Pll> mp[2];
vector<ll> x, y;

void dfs(int id, int i, int N, ll X, ll Y){
  if(i == N)mp[id][idx++] = mk(X, Y);
  else{
    dfs(id, i + 1, N, X, Y);
    dfs(id, i + 1, N, X + x[i], Y + y[i]);
    dfs(id, i + 1, N, X - x[i], Y - y[i]);
  }
}

template<typename T, typename E>
struct SegmentTree_ {
  function<T(T, T)> f;
  function<T(T, E)> g;
  int n;
  T def;
  vector<T> vec;
  SegmentTree_(){}
  SegmentTree_(int n_, function<T(T, T)> f_, function<T(T, E)> g_, T def_, vector<T> v=vector<T>()){
    f = f_;
    g = g_;
    def = def_;

    // initialize vector
    n = 1;
    while(n < n_){
      n *= 2;
    }
    vec = vector<T>(2*n -1, def);

    // initialize segment tree
    for(int i = 0; i < v.size(); i++){
      vec[i + n - 1] = v[i];
    }
    for(int i = n - 2; i >= 0; i--){
      vec[i] = f(vec[2*i+1], vec[2*i+2]);
    }
  }
  void update(int k, const E &val){
    k = k + n - 1;
    vec[k] = g(vec[k], val);
    while(k > 0){
      k = (k - 1) / 2;
      vec[k] = f(vec[2*k+1], vec[2*k+2]);
    }
  }
  // [l, r) -> [a, b) (at k)
  T query(int a, int b, int k, int l, int r){
    if(r <= a || b <= l)return def;
    if(a <= l && r <= b)return vec[k];
    T ld = query(a, b, 2*k+1, l, (l+r)/2);
    T rd = query(a, b, 2*k+2, (l+r)/2, r);
    return f(ld, rd);
  }
  T query(int a, int b){
    return query(a, b, 0, 0, n);
  }
};

template<typename T, typename E>
using SegmentTree = struct SegmentTree_<T, E>;
using SegmentTreeI = SegmentTree<int, int>;
using SegmentTreeL = SegmentTree<long long, long long>;

int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(20);
  INT(n); LL(d);
  x.resize(n); y.resize(n); rep(i, n)cin >> x[i] >> y[i];
  int b = power3(n/2);
  int bn = power3(n-n/2);
  mp[0].resize(b); mp[1].resize(bn);
  idx = 0;
  dfs(0, 0, n / 2, 0, 0);
  idx = 0;
  dfs(1, n/2, n, 0, 0);
  sort(all(mp[0]));
  sort(all(mp[1]));
  //vector<Pll> tmp;
  //rep(i, sz(mp[1])){
  //  if(i + 1 < sz(mp[1]) && mp[1][i].first == mp[1][i+1].first)continue;
  //  tmp.pb(mp[1][i]);
  //}
  //swap(mp[1], tmp);
  ll res = 0;
  //multiset<ll> st;
  vector<ll> vy(sz(mp[1])); rep(i, sz(mp[1]))vy[i] = mp[1][i].second;
  SegmentTreeL seg = SegmentTreeL(sz(mp[1]), [](ll a, ll b){return max(a, b);},
                                  [](ll a,ll b){return b;}, - linf, vy);
  int l = 0, r = 0;
  reverse(all(mp[0]));
  for(int i = 0; i < sz(mp[0]); i++){
    ll xd = mp[0][i].first;
    ll yd = mp[0][i].second;
    for(; r < sz(mp[1]); ++r){
    if(mp[1][r].first > d - xd)break;
    //st.insert(mp[1][r].second);
    }
    for(; l < sz(mp[1]); ++l){
      if(mp[1][l].first >= - d - xd)break;
      //st.erase(st.find(mp[1][l].second));
    }
    //if(sz(st))res = max(res, (*(st.rbegin())) + yd);
    res = max(res, yd + seg.query(l, r));
  }
  cout << res << endl;
  return 0;
}



Measured memory_bytes: 937728