//v / wが大きいほうから探索　→　分岐限定で枝刈り
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;

struct Baggage {
	double key;
	long long v, w;
	Baggage() {}
	Baggage(long long v, long long w) {
		this->v = v;
		this->w = w;
		key = (double)v / w;
	}
	bool operator>(const Baggage &r) const {
		return key > r.key;
	}
};

int n;
long long w;
Baggage bag[5000];
long long maxSumV;

void maxV(int id, long long remW, long long sumV) {
	if (id == n) {
		maxSumV = max(maxSumV, sumV);
		return;
	}
	if (sumV + remW * bag[id].key <= maxSumV) {
		return;
	}
	if (remW >= bag[id].w) {
		maxV(id + 1, remW - bag[id].w, sumV + bag[id].v);
	}
	maxV(id + 1, remW, sumV);
}

int main() {
	int i;
	
	cin >> n >> w;
	for (i = 0; i < n; i++) {
		long long v, w;
		cin >> v >> w;
		bag[i] = Baggage(v, w);
	}
	sort(bag, bag + n, greater<Baggage>());
	maxV(0, w, 0);
	cout << maxSumV << endl;
	return 0;
}