## implementation

#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; (i) < int(n); ++ (i))
#define ALL(x) begin(x), end(x)
using ll = long long;
using namespace std;
template <class T> inline void chmax(T & a, T const & b) { a = max(a, b); }

ll knapsack_problem_branch_and_bound(int n, ll max_w, vector<ll> const & a_v, vector<ll> const & a_w) {
vector<ll> v(n), w(n); {
vector<int> xs(n);
iota(ALL(xs), 0);
sort(ALL(xs), [&](int i, int j) {
return a_v[i] *(double) a_w[j] > a_v[j] *(double) a_w[i];
});
REP (i, n) {
v[i] = a_v[xs[i]];
w[i] = a_w[xs[i]];
}
}
ll ans = 0;
function<void (int, ll, ll)> go = [&](int i, ll cur_v, ll cur_w) {
if (max_w < cur_w) return; // not executable
if (i == n) {
chmax(ans, cur_v);
return; // terminate
}
ll lr_v = cur_v; // linear relaxation
ll lr_w = cur_w;
int j = i;;
for (; j < n and lr_w + w[j] <= max_w; ++ j) { // greedy
lr_w += w[j];
lr_v += v[j];
}
if (lr_w == max_w or j == n) {
chmax(ans, lr_v);
return; // accept greedy
}
double lr_ans = lr_v + v[j] * ((max_w - lr_w) /(double) w[j]);
if (lr_ans <= ans) return; // bound
go(i + 1, cur_v + v[i], cur_w + w[i]);
go(i + 1, cur_v,        cur_w       );
};
go(0, 0, 0);
return ans;
}

int main() {
int n; ll max_w; cin >> n >> max_w;
vector<ll> v(n), w(n); REP (i, n) cin >> v[i] >> w[i];
ll result = knapsack_problem_branch_and_bound(n, max_w, v, w);
cout << result << endl;
return 0;
}