#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int mxN = 2e5 + 5;
const ll inf = 1e18;
int v[mxN], c[mxN], comp[mxN];
ll ans = -inf;
int n, m, lptr, rptr;
int bx[mxN];
ll by[mxN];
void upd(int i, int x, int y) {
for (; i <= n; i += i & (-i)) bx[i] += x, by[i] += y;
}
pair<int, ll> query(int i) {
int sx = 0;
ll sy = 0;
for (; i > 0; i -= i & (-i)) sx += bx[i], sy += by[i];
return {sx, sy};
}
ll query() {
int cur = 0, sumx = 0;
for (int i = 18; i >= 0; i--) {
if (cur + (1 << i) <= n && sumx + bx[cur + (1 << i)] < m) {
sumx += bx[cur + (1 << i)];
cur += (1 << i);
}
}
auto [fx, fy] = query(cur + 1);
if (fx != m) return -inf;
return fy;
}
void add(int i) {
if (!i) return;
upd(comp[i], 1, v[i]);
}
void rem(int i) {
if (!i) return;
upd(comp[i], -1, -v[i]);
}
ll get(int l, int r) {
while (lptr > l) add(--lptr);
while (rptr < r) add(++rptr);
while (rptr > r) rem(rptr--);
while (lptr < l) rem(lptr++);
return query();
}
void solve(int l, int r, int optl, int optr) {
if (l > r) return;
int m = (l + r) >> 1;
int opt;
ll best = -inf;
for (int i = max(m, optl); i <= optr; i++) {
if (best < get(m, i) + 2 * (c[m] - c[i])) {
best = get(m, i) + 2 * (c[m] - c[i]);
opt = i;
}
}
ans = max(ans, best);
if (best == -inf) {
solve(l, m - 1, optl, optr);
} else {
solve(l, m - 1, optl, opt);
solve(m + 1, r, opt, optr);
}
}
void testCase() {
cin >> n >> m;
vector<int> all;
for (int i = 1; i <= n; i++) {
cin >> v[i] >> c[i];
all.push_back(v[i]);
}
{
vector<int> ord(n);
iota(ord.begin(), ord.end(), 1);
sort(ord.begin(), ord.end(), [&](int i, int j) { return c[i] < c[j]; });
vector<int> nv(n + 1), nc(n + 1);
for (int i = 0; i < n; i++) nv[i + 1] = v[ord[i]], nc[i + 1] = c[ord[i]];
for (int i = 1; i <= n; i++) c[i] = nc[i], v[i] = nv[i];
}
sort(all.rbegin(), all.rend());
map<int, int> mp;
for (int i = n - 1; i >= 0; i--) mp[all[i]] = i + 1;
vector<bool> done(all.size());
for (int i = 1; i <= n; i++) {
comp[i] = mp[v[i]]++;
}
solve(1, n, 1, n);
cout << ans << "\n";
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
testCase();
return 0;
}
