#include <bits/stdc++.h>
using namespace std;
#define int long long
#define form2(i, a, b) for (int i = (a); i < (b); ++i)
#define ford2(i, a, b) for (int i = (a-1); i >= b; --i)
#define form(i, n) form2(i, 0, n)
#define ford(i, n) ford2(i, n, 0)
#define chmax(x, v) x = max(x, (v))
#define chmin(x, v) x = min(x, (v))
#define fi first
#define se second
const long long BIG = 1000000000000000000LL;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
void cpr(string s, vector<int> v)
{ int i = 0; for (char c : s) { if (c == '$') cout << v[i++]; else cout << c; } cout << '\n'; }
void cpr(string s) { cpr(s, {}); }
void solve();
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
solve();
return 0;
}
const int borne = 201*1000;
int nbPieces, nbVoulu;
pii pieces[borne];
int rep = -BIG;
pii st[4*borne];
int otn[borne];
int gt[borne];
void upd(int nod, int il, int ir, int cible, int val)
{
if (il == ir) {
assert(il == cible);
st[nod].fi += val*otn[il];
st[nod].se += val;
return;
}
int im = (il+ir)/2;
if (cible <= im) upd(2*nod, il, im, cible, val);
else upd(2*nod+1, im+1, ir, cible, val);
st[nod].fi = st[2*nod].fi + st[2*nod+1].fi;
st[nod].se = st[2*nod].se + st[2*nod+1].se;
}
int cl=0, cr=0;
pii walk(int nod, int il, int ir, int k)
{
if (k == 0 || st[nod].se == 0) return {0,0};
if (st[nod].se <= k) {
return st[nod];
}
int im = (il+ir)/2;
pii ret = walk(2*nod+1, im+1, ir, k);
k -= ret.se;
pii ret2 = walk(2*nod, il, im, k);
ret.fi += ret2.fi;
ret.se += ret2.se;
return ret;
}
int func(int deb, int fin)
{
if (fin < deb+nbVoulu-1) return -BIG;
int ca = 2*(pieces[deb].fi - pieces[fin].fi);
int nod = 1;
while (cl < deb) { upd(nod, 0, nbPieces-1, gt[cl], -1); ++cl; } // suppr
while (cl > deb) { --cl; upd(nod, 0, nbPieces-1, gt[cl], 1); } // rajout
while (cr > fin) { upd(nod, 0, nbPieces-1, gt[cr], -1); --cr; } // suppr
while (cr < fin) { ++cr; upd(nod, 0, nbPieces-1, gt[cr], 1); } // rajout
assert(st[1].se == (fin-deb+1));
ca += walk(nod, 0, nbPieces-1, nbVoulu).fi;
return ca;
}
void calc(int il, int ir, int kl, int kr)
{
if (il > ir) return;
int im = (il+ir) / 2;
int ca = -BIG-1, opt = kl;
form2(k, kl, min(kr, ir)+1) {
int nv = func(k, im);
if (nv > ca) {
ca = nv;
opt = k;
}
}
chmax(rep, ca);
calc(il, im-1, kl, opt);
calc(im+1, ir, opt, kr);
}
map<int, int> nto;
void solve()
{
cin >> nbPieces >> nbVoulu;
form(i, nbPieces) {
// val, coul
cin >> pieces[i].fi >> pieces[i].se;
}
sort(pieces, pieces+nbPieces);
vector<pair<pii, int>> oth;
form(i, nbPieces) {
// devient coul, val
swap(pieces[i].fi, pieces[i].se);
oth.push_back({pieces[i], i});
}
sort(oth.begin(), oth.end());
sort(pieces, pieces+nbPieces);
form(i, nbPieces) { gt[i] = oth[i].se; otn[gt[i]] = pieces[i].se; }
sort(pieces, pieces+nbPieces);
upd(1, 0, nbPieces-1, gt[0], 1);
calc(0, nbPieces-1, 0, nbPieces-1);
cout << rep << "\n";
}
