#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;

// chmax, chmin
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

template <typename T>
function<T(T, T)> op_max = [](T a, T b) -> T { return max(a, b); };
template <typename T>
function<T(T, T)> op_min = [](T a, T b) -> T { return min(a, b); };

template <typename T>
function<T(T, T)> op_sum = [](T a, T b) -> T { return a + b; };

namespace detail {
template <typename T, std::size_t NDIMS>
struct vector_builder {
  using type = std::vector<typename vector_builder<T, NDIMS - 1>::type>;

  static type make(std::vector<std::size_t> dims, const T& v = {}) {
    const auto vec = std::vector<T>(dims.empty() ? 0 : dims.back(), v);
    if (!dims.empty()) dims.pop_back();
    return vector_builder<std::vector<T>, NDIMS - 1>::make(dims, vec);
  }
};

template <typename T>
struct vector_builder<T, 1> {
  using type = std::vector<T>;

  static type make(std::vector<std::size_t> dims, const T& v = {}) {
    return type(dims.empty() ? 0 : dims.back(), v);
  }
};
}  // namespace detail

template <typename T, typename... SIZE_T>
auto exvector(const T& v, SIZE_T... dims) {
  static_assert(sizeof...(dims) != 0, "invalid dimension");
  std::vector<std::size_t> vec_dims{dims...};
  return detail::vector_builder<T, sizeof...(dims)>::make(vec_dims, v);
}

using namespace std;
//********************  dumps ************************//

template <typename T>
void dump(const T& data, vector<int>& iter) {
  cout << data << " ";
}
template <typename T>
void dump(const vector<T>& data, vector<int>& iter) {
  for (auto elem : data) dump(elem, iter);
  cout << endl;
}

template <typename T>
void dump(const vector<vector<T>>& data, vector<int>& iter) {
  for (auto elem : iter) {
    cout << "[" << elem << "]";
  }
  cout << endl;
  for (int i = 0; i < data.size(); i++) {
    iter.push_back(i);
    dump(data[i], iter);
    iter.pop_back();
  }
  cout << endl;
}

template <typename T>
void dump(const vector<T>& data, int dummy) {
  for (int i = 0; i < data.size(); i++) {
    cout << "[" << i << "] " << data[i] << endl;
  }
}
template <typename T>
void dump(const T& data) {  // T : data, U = base type val.
  vector<int> iter;
  dump(data, iter);
}
///////////////////////////////////////////////

LL dfs(vector<LL> &w, vector<vector<LL>> &vs, int iter, 
       LL W, PII cur) {
  if(iter==w.size()) {
    if(cur.first <= W) return cur.second;
    return 0;
  }
  LL ans = dfs(w, vs, iter+1, W, cur);
  LL sum = 0;
  for(int i=0; i<vs[iter].size(); i++) {
    PII next = cur;
    sum += vs[iter][i];
    next.first = cur.first + (i+1) * w[iter];
    next.second = cur.second + sum;
    chmax(ans, dfs(w, vs, iter+1, W, next));

  }
  return ans;


}


int main() {
  LL N, W;
  cin >> N >> W;
  map<LL, vector<LL> > data;
  for(int i=0; i<N; i++) {
    LL w, v;
    cin >> w >> v;
    data[w].push_back(v);
  }
  vector<vector<LL> > vs;
  vector<LL> w;
  for(auto elem : data) {
    w.push_back(elem.first);
    vs.push_back(elem.second);
  }
  for(auto &v: vs) {
    sort(v.begin(), v.end());
    reverse(v.begin(), v.end());
  }
  LL ans = dfs(w, vs, 0, W, PII(0,0));
  cout << ans << endl;

  return 0;
}


Measured memory_bytes: 256