#include <algorithm>
#include <array>
#include <bitset>
#include <complex>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <queue>

using namespace std;

struct BoolName : numpunct<char> {
  string t, f;
  BoolName (string t = "Yes", string f = "No") : t(t), f(f) {}
  string do_truename() const {return t;}
  string do_falsename() const {return f;}
};

struct Initializer {
  Initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15) << boolalpha;
    cout.imbue(locale(cout.getloc(), new BoolName));
  }
} initializer;

template<typename T> istream& operator>>(istream &s, vector<T> &v) {
  for (T &t : v) s >> t;
  return s;
}

template<typename T> ostream& operator<<(ostream &s, const vector<T> &v) {
  for (const T &t : v) s << t << endl;
  return s;
}

void set_bool_name(string t, string f) {
  cout.imbue(locale(cout.getloc(), new BoolName(t, f)));
}

template<typename T> bool chmin(T& a, T b) {return a > b ? a = b, true : false;}

template<typename T> bool chmax(T& a, T b) {return a < b ? a = b, true : false;}

template<typename T> void sort(vector<T>& v) {sort(v.begin(), v.end());}

template<typename T> T min(const vector<T>& v) {return *min_element(v.begin(), v.end());}

template<typename T> T max(const vector<T>& v) {return *max_element(v.begin(), v.end());}

template<typename T> int min_element(vector<T>& v) {return min_element(v.begin(), v.end()) - v.begin();}

template<typename T> int max_element(vector<T>& v) {return max_element(v.begin(), v.end()) - v.begin();}

template<typename T, typename Function> void sort(vector<T>& v, Function func) {sort(v.begin(), v.end(), func);}

template<typename T> void rsort(vector<T>& v) {sort(v.rbegin(), v.rend());}

template<typename T> void reverse(vector<T>& v) {reverse(v.begin(), v.end());}

template<typename T> void unique(vector<T>& v) {v.erase(unique(v.begin(), v.end()), v.end());}

template<typename T> void nth_element(vector<T>& v, int n) {nth_element(v.begin(), v.begin() + n, v.end());}

template<typename T> bool next_permutation(vector<T>& v) {return next_permutation(v.begin(), v.end());}

template<typename T> int find(vector<T>& v, T t) {return find(v.begin(), v.end(), t) - v.begin();}

template<typename T, typename S> int in(T v, S t) {return find(v.begin(), v.end(), t) != v.end();}

template<typename T> int lower_bound(vector<T>& v, T t) {return lower_bound(v.begin(), v.end(), t) - v.begin();}

template<typename T> int upper_bound(vector<T>& v, T t) {return upper_bound(v.begin(), v.end(), t) - v.begin();}

template<typename T, typename S = typename T::value_type, typename BinaryOperation> S accumulate(const T& v, S init, BinaryOperation func) {
  return accumulate(v.begin(), v.end(), init, func);
}

template<typename T, typename S = typename T::value_type> S accumulate(const T& v, S init = 0) {
  return accumulate(v.begin(), v.end(), init);
}

template<typename T> void adjacent_difference(vector<T>& v) {adjacent_difference(v.begin(), v.end(), v.begin());}

template<typename T> void adjacent_difference(vector<T>& v, vector<T>& u) {adjacent_difference(v.begin(), v.end(), u.begin());}

template<typename T> vector<T> partial_sum(const vector<T>& v) {
  vector<T> u(v.size());
  partial_sum(v.begin(), v.end(), u.begin());
  return u;
}

template<typename T> T inner_product(vector<T>& v, vector<T>& u) {return inner_product(v.begin(), v.end(), u.begin(), T(0));}

template<typename T> int count(const T& v, typename T::value_type t) {return count(v.begin(), v.end(), t);}

template<typename T, typename Function> int count_if(const vector<T>& v, Function func) {return count_if(v.begin(), v.end(), func);}

template<typename T, typename Function> void remove_if(vector<T>& v, Function func) {v.erase(remove_if(v.begin(), v.end(), func), v.end());}

template<typename T, typename Function> bool all_of(vector<T> v, Function func) {return all_of(v.begin(), v.end(), func);}

template<typename T, typename Function> bool any_of(vector<T> v, Function func) {return any_of(v.begin(), v.end(), func);}

template<typename T, typename Function> bool none_of(vector<T> v, Function func) {return none_of(v.begin(), v.end(), func);}

template<typename T> vector<T> subvector(vector<T>& v, int a, int b) {return vector<T>(v.begin() + a, v.begin() + b);}

template<typename T> int kinds(const T& v) {return set<typename T::value_type>(v.begin(), v.end()).size();}

template<typename T> map<typename T::value_type, int> count_kinds(const T& v) {
  map<typename T::value_type, int> res;
  for (const auto& i : v) ++res[i];
  return res;
}

template<typename T> void iota(vector<T>& v, T t = 0) {iota(v.begin(), v.end(), t);}

template<typename T> bool is_sorted(const vector<T>& v) {return is_sorted(v.begin(), v.end());}

int w0;
vector<int> a[4];

int64_t solve(int k, int w) {
  if (k == 4) return 0;
  int64_t res = solve(k + 1, w), r = 0;
  for (int i = 0; i < int(a[k].size()); ++i) {
    w -= w0 + k;
    if (w < 0) break;
    r += a[k][i];
    chmax(res, r + solve(k + 1, w));
  }
  return res;
}

int main() {
  int n, x;
  cin >> n >> x;
  vector<int> w(n), v(n);
  for (int i = 0; i < n; ++i) cin >> w[i] >> v[i];
  w0 = w[0];
  for (int i = 0; i < n; ++i) a[w[i] - w0].emplace_back(v[i]);
  for (int i = 0; i < 4; ++i) rsort(a[i]);
  cout << solve(0, x) << endl;
}



Measured memory_bytes: 256