#include<bits/stdc++.h>
using namespace std;
typedef long long llint;
typedef pair <int, int> pi;
const int MAXN = 200005;
const llint INF = 1000000000000000000LL;
llint n, m, sum, sol = -INF;
pi p[MAXN];
multiset <int> st;
vector <pi> v;
bool cmp (pi a, pi b) {
return a.second < b.second;
}
void ubaci (int val) {
//cout << "ubaci " << val << endl;
st.insert(val);
sum += val;
if (st.size() > m - 2) {
auto it = st.begin();
sum -= *it;
v.push_back({val, *it});
st.erase(it);
} else {
v.push_back({val, 0});
}
}
void rollback () {
int val = v.back().first, mn = v.back().second;
//cout << "rollback " << val << " " << mn << endl;
v.pop_back();
if (mn) st.insert(mn);
st.erase(st.find(val));
sum += mn - val;
}
void calc (int lef, int rig, int lo, int hi) {
if (lef > rig) return;
//cout << "calc " << lef << " " << rig << " " << lo << " " << hi << endl;
int mid = (lef + rig) / 2;
//cout << "mid je " << mid << endl;
for (int i = max(hi + 1, lef); i < mid; i++) {
ubaci(p[i].first);
}
llint res = -INF, piv = -1;
for (int i = min(mid - 1, hi); i >= lo; i--) {
if (st.size() == m - 2) {
llint tmp = sum + p[i].first + p[i].second;
if (tmp > res) {
res = tmp;
piv = i;
}
}
ubaci(p[i].first);
}
//cout << "piv je " << piv << endl;
sol = max(sol, res + p[mid].first - p[mid].second);
for (int i = lo; i <= min(mid - 1, hi); i++) rollback();
if (hi < mid) ubaci(p[mid].first);
calc(mid + 1, rig, piv, hi);
if (hi < mid) rollback();
for (int i = max(hi + 1, lef); i < mid; i++) rollback();
for (int i = piv + 1; i <= min(lef - 1, hi); i++) ubaci(p[i].first);
calc(lef, mid - 1, lo, piv);
for (int i = piv + 1; i <= min(lef - 1, hi); i++) rollback();
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n >> m;
for (int i = 0; i < n; i++) {
cin >> p[i].first >> p[i].second;
p[i].second *= 2;
}
sort(p, p + n, cmp);
calc(m - 1, n - 1, 0, n - 1);
cout << sol;
return 0;
}
