//v / wが大きいほうから再帰探索　→　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;

long long maxV(int id, long long remW, long long sumV) {
	if (id == n) {
		maxSumV = max(maxSumV, sumV);
		return 0;
	}
	if (remW * bag[id].key <= maxSumV - sumV) {	//戻り値の上界<=maxSumVが更新されるような戻り値の下界
		return 0;
	}
	long long res, ret = 0;
	if (remW >= bag[id].w) {
		res = maxV(id + 1, remW - bag[id].w, sumV + bag[id].v) + bag[id].v;
		ret = max(res, ret);
	}
	res = maxV(id + 1, remW, sumV);
	ret = max(res, ret);
	return ret;
}

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>());
	cout << maxV(0, w, 0) << endl;
	return 0;
}