#include <bits/stdc++.h>
using namespace std;
#define ff endl
#define lf "\n"
#define fi first
#define se second
#define _ << ' ' <<
#define all(x) begin(x),end(x)
#define rall(x) rbegin(x),rend(x)
#ifdef DEBUG
constexpr bool IS_DEBUG = 1;
#define infor(fmt, ...) do { print(stderr, fmt, ##__VA_ARGS__); } while(0)
#define infof(fmt, ...) do { println(stderr, fmt, ##__VA_ARGS__); } while(0)
#else
constexpr bool IS_DEBUG = 0;
#define infor(fmt, ...)
#define infof(fmt, ...)
#endif
using ll = long long;
using pll = pair<ll, ll>;
using pii = pair<int, int>;
template<typename... Args>
using vec = vector<Args...>;
mt19937 timmy_loves_gambling(73);
constexpr ll INF = 1e18;
int main(void) {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int N; ll M;
cin >> N >> M;
vec<ll> V0(N), W0(N);
for(int i = 0; i < N; ++i) {
cin >> V0[i] >> W0[i];
}
vec<int> ord(N);
iota(all(ord), 0);
sort(all(ord), [&](int i, int j) -> bool {
return W0[i] == W0[j] ? V0[i] > V0[j] : W0[i] < W0[j];
});
vec<ll> V(N), W(N);
for(int i = 0; i < N; ++i) {
V[i] = V0[ord[i]];
W[i] = W0[ord[i]];
}
V0.clear();
V0.shrink_to_fit();
W0.clear();
W0.shrink_to_fit();
ord.clear();
ord.shrink_to_fit();
vec<int> L, R;
L.emplace_back(0);
for(int i = 1; i < N; ++i) {
if(W[i] > W[i - 1]) {
R.emplace_back(i);
L.emplace_back(i);
}
}
R.emplace_back(N);
const int K = L.size();
W.emplace_back(INF);
vec<ll> bcnt(K);
for(int k = K - 1; k >= 0; k--) {
bcnt[k] = M / W[L[k]];
M %= W[L[k]];
}
ll ans = 0;
for(int k = 0; k < K; ++k) {
ll m = bcnt[k];
infof("k = {} | W[k] = {} | m = {}", k, W[L[k]], m);
vec<pll> p;
for(int i = 0; i <= k; ++i) {
ll sz = W[L[k]] / W[L[i]];
for(int l = L[i]; l < R[i]; l += sz) {
ll s = 0;
for(int j = 0; j < min(sz, (ll)R[i] - l); ++j) {
s += V[l + j];
}
p.emplace_back(s, i);
}
}
sort(rall(p));
infof("p: {}", p);
for(int i = 0; i < min(m, (ll)p.size()); ++i) {
auto [x, j] = p[i];
ans += x;
L[j] += W[L[k]] / W[L[j]];
}
}
cout << ans << lf;
}
