#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
ifstream cin("rucsac.in");
ofstream cout("rucsac.out");
int n, g;
int v[5001];
int bestprof = -1;
struct obiect
{
	int gr;
	int v;
	bool operator >	(const obiect x) const
	{
		return ((this->v * x.gr) < (x.v*this->gr));
	}
	bool operator < (const obiect x) const
	{
		return ((this->v * x.gr) >(x.v * this->gr));
	}
};
obiect rest[5001];
int ginit = 0;
int profinit = 0;
vector <obiect>o;
void bkt(int level)
{
    bestprof = max(profinit, bestprof);
	if (level > n || ginit==g )
	{
		;
	}
	else
	{
		if (profinit + min(rest[level].gr,g-ginit)*rest[level].v> bestprof && ginit+o[level].gr<=g)
		{
			    ginit+=o[level].gr;
				profinit+=o[level].v;
				bkt(level + 1);
				ginit -= o[level].gr;
				profinit-=o[level].v;
		}
		if (profinit+rest[level+1].v*min(rest[level+1].gr,g-ginit)>bestprof)
		{
		    bkt(level+1);
		}
	}

}
int main()
{
	cin >> n >> g;
	for (int i = 0; i < n; i++)
	{
		int gr, v;
			cin >> gr >> v;
			o.push_back({ gr,v});
	}
	sort(o.begin(),o.end());
    
	rest[n].v=0;
	rest[n].gr=0;
	for (int i = n - 1; i >= 0; i--)
	{
		rest[i].v= rest[i + 1].v + o[i].v;
		rest[i].gr=rest[i+2].gr+o[i].gr;
	}
	bkt(0);
	cout << bestprof;
	
}