#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

const int N = 5000;
int n;
long long C;
long long V[N];
long long W[N];
int p[N];

long long ans;

// ***************************........
// [--------greedy-----------]
//
// **********************.*...*.**....
// [--------core---------]
void dfs(long long w, long long v, int k) {
  if (w > C) return;
  ans = max(ans, v);

  for (int i = k; i < n; i++) {
    // You can estimate the upper bound by Rational Knapsack problem.
    if (v + (double)V[ p[i] ] / W[ p[i] ] * (C - w) < ans - 1e-8) break;
    dfs(w + W[ p[i] ], v + V[ p[i] ], i + 1);
  }
}

int main() {
  cin >> n >> C;

  for (int i = 0; i < n; i++) {
    cin >> V[i] >> W[i];
    p[i] = i;
  }

  sort(p, p + n, [&](int i, int j) {
   return (double)V[i] / W[i] > (double)V[j] / W[j]; 
  });

  long long v = 0;
  long long w = 0;
  int k = 0;
  while (k < n) {
    v += V[ p[k] ];
    w += W[ p[k] ];
    k++;
    if (w > C) break;
  }

  for (int i = k - 1; i >= 0; i--) {
    w -= W[ p[i] ];
    v -= V[ p[i] ];
    if (v + (double)V[ p[i] ] / W[ p[i] ] * (C - w) < ans - 1e-8) break;
    dfs(w, v, i);
  }

  cout << ans << endl;
}