#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

long long N, W, v[5009], w[5009]; vector<pair<long long, long long>>vec, vec2;

int main() {
	cin >> N >> W;
	for (int i = 1; i <= N; i++) {
		cin >> v[i] >> w[i];
	}
	vec.push_back(make_pair(0, 0));
	for (int i = 1; i <= N; i++) {
		for (int j = 0; j < vec.size(); j++) {
			vec2.push_back(vec[j]);
			vec2.push_back(make_pair(vec[j].first + w[i], vec[j].second + v[i]));
		}
		sort(vec2.begin(), vec2.end()); vec.clear();
		long long maxn = -1;
		for (int j = 0; j < vec2.size(); j++) {
			if (maxn < vec2[j].second) {
				maxn = vec2[j].second;
				vec.push_back(vec2[j]);
			}
		}
		vec2.clear();
	}
	long long T = 0;
	for (int i = 0; i < vec.size(); i++) { if (vec[i].first <= W) T = vec[i].second; }
	cout << T << endl;
	return 0;
}