#define _CRT_SECURE_NO_WARNINGS
#define _SCL_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <utility>
#include <algorithm>
#include <functional>
#include <cmath>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <iomanip>
#include <sstream>
#include <bitset>
#include <limits>
#include <numeric>
#include <valarray>
#include <fstream>

using namespace std;
typedef unsigned int uint;
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<LL, LL> PP;
#define REP(i,a,n) for(LL i = (a); i < (LL)(n); ++i)
#define REM(i,a,n) for(LL i = ((n) - 1); i >= (a); --i)
#define FLOAT fixed << setprecision(16)
#define SPEEDUP {cin.tie(0); ios::sync_with_stdio(false);}
const int INF = 0x3FFFFFFF;
const LL INFLL = 0x3FFFFFFF3FFFFFFF;
const double INFD = 1.0e+308;
const string INFSTR = "\x7f";
const double EPS = 1.0e-9;

void YesNo(bool b) { cout << (b ? "Yes" : "No") << endl; }
void YESNO(bool b) { cout << (b ? "YES" : "NO") << endl; }
template <class T, class U>
istream& operator>>(istream& ist, pair<T, U>& right) { return ist >> right.first >> right.second; }
template <class T, class U>
ostream& operator<<(ostream& ost, const pair<T, U>& right) { return ost << right.first << ' ' << right.second; }
template <class T, class TCompatible, size_t N>
void Fill(T(&dest)[N], const TCompatible& val) { fill(dest, dest + N, val); }
template <class T, class TCompatible, size_t M, size_t N>
void Fill(T(&dest)[M][N], const TCompatible& val) { for (int i = 0; i < M; ++i) Fill(dest[i], val); }
template<class T>
T Compare(T left, T right) { return left > right ? 1 : (left < right ? -1 : 0); }
istream& Ignore(istream& ist) { string s; ist >> s; return ist; }
bool Inside(int i, int j, int h, int w) { return i >= 0 && i < h && j >= 0 && j < w; }
// all_of
// partial_sum, adjacent_difference

#ifdef ONLY_MY_ENVIR
#include "IntMod.h"
#include "Union_Find.h"
#include "Graph.h"
#include "Range.h"
#include "Global.h"
#include "Flow_Solver.h"
#include "Tree.h"
#include "Suffix_Array.h"
#include "Geometry.h"
#include "Matrix.h"
#endif

#ifdef __GNUC__
typedef __int128 LLL;
istream& operator>> (istream& ist, __int128& val) { LL tmp;  ist >> tmp; val = tmp; return ist; }
ostream& operator<< (ostream& ost, __int128 val) { LL tmp = val; ost << tmp; return ost; }
#endif

#if 1234567891
#include <array>
#include <random>
#include <unordered_set>
#include <unordered_map>
template<typename T>
using PriorityQ = priority_queue<T, vector<T>, greater<T> >;	// コスト小を優先
#endif

LL N, K;
int main() {
	cin >> N >> K;
	map<LL, vector<LL>> M;

	REP(i, 0, N) {
		int a, b;
		cin >> a >> b;
		M[a].push_back(b);
	}

	LL w0 = M.begin()->first;
	vector<LL> V[4];
	REP(c, 0, 4) {
		V[c] = M[w0 + c];
	}
	REP(i, 0, 4) {
		sort(V[i].begin(), V[i].end(), greater<LL>());
	}

	LL mx = 0;
	REP(i, 0, V[0].size() + 1) {
		REP(j, 0, V[1].size() + 1) {
			REP(k, 0, V[2].size() + 1) {
				REP(l, 0, min(N - (i + j + k), (LL)V[3].size()) + 1) {
					if (w0 * i + (w0 + 1) * j + (w0 + 2) * k + (w0 + 3) * l > K) continue;
					LL sum = 0;

					REP(ii, 0, i) sum += V[0][ii];
					REP(jj, 0, j) sum += V[1][jj];
					REP(kk, 0, k) sum += V[2][kk];
					REP(ll, 0, l) sum += V[3][ll];
					mx = max(mx, sum);
				}
			}
		}
	}
	cout << mx << endl;
	return 0;
}

Measured memory_bytes: 256