#include "bits/stdc++.h"
#define int long long
#define all(v) v.begin() , v.end()
#define sz(a) (int)a.size()
using namespace std;
const int INF = 1e18;
const int N = 2e5 + 5;
struct Node{
Node* lc;
Node* rc;
int cnt, sub;
Node(){
lc = rc = NULL;
cnt = sub = 0;
}
};
struct PST{
int n, def;
vector<Node*> roots;
Node* build(int l, int r){
if(l == r) return new Node();
int m = (l + r) / 2;
Node* res = new Node();
res -> lc = build(l, m);
res -> rc = build(m + 1, r);
return res;
}
Node* update(Node* rt, int l, int r, int ind, int u){
if(l == r){
Node* res = new Node();
res -> sub = rt -> sub + 1;
res -> cnt = rt -> cnt + u;
return res;
}
Node* res = new Node();
int m = (l + r) / 2;
if(ind <= m){
res -> lc = update(rt -> lc, l, m, ind, u);
res -> rc = rt -> rc;
}
else{
res -> lc = rt -> lc;
res -> rc = update(rt -> rc, m + 1, r, ind, u);
}
res -> sub = res -> lc -> sub + res -> rc -> sub;
res -> cnt = res -> lc -> cnt + res -> rc -> cnt;
return res;
}
PST(int _n, int _def){
n = _n, def = _def;
roots.push_back(build(1, n));
}
void add_index(int ind, int u){
roots.push_back(update(roots.back(), 1, n, ind, u));
}
int get_sum(int l, int r, int k){
Node* pl = roots[l - 1];
Node* pr = roots[r];
int res = 0;
while(pl -> lc != NULL){
if((pr -> rc -> sub) - (pl -> rc -> sub) >= k){
pr = pr -> rc;
pl = pl -> rc;
}
else{
res += (pr -> rc -> cnt) - (pl -> rc -> cnt);
k -= (pr -> rc -> sub) - (pl -> rc -> sub);
pr = pr -> lc;
pl = pl -> lc;
}
}
if(k) res += k * ((pr -> cnt - pl -> cnt) / (pr -> sub - pl -> sub));
return res;
}
};
int n, k, ans = -INF;
map<int,int> mp;
array<int,2> v[N];
PST pst = PST(1,1);
void calc(int l, int r, int optl, int optr){
if(l > r) return;
int m = (l + r) / 2;
int res = -INF, opt = -1;
for(int i = max(optl, m + k - 1); i <= optr; i++){
if(v[m][1] + v[i][1] + v[m][0] - v[i][0] + pst.get_sum(m + 1, i - 1, k - 2) > res){
res = v[m][1] + v[i][1] + v[m][0] - v[i][0] + pst.get_sum(m + 1, i - 1, k - 2);
opt = i;
}
}
ans = max(ans, res);
calc(l, m - 1, optl, opt), calc(m + 1, r, opt, optr);
}
void _(){
cin >> n >> k;
for(int i=1;i<=n;i++){
int a, b;
cin >> a >> b;
v[i] = {2 * b, a};
mp[a] = 1;
}
int p=0;
for(auto x:mp) mp[x.first]=++p;
sort(v+1,v+n+1);
pst = PST(n,0);
for(int i=1;i<=n;i++) pst.add_index(mp[v[i][1]], v[i][1]);
calc(1, n - k + 1, 1, n);
cout << ans << '\n';
}
int32_t main(){
cin.tie(0); ios::sync_with_stdio(0);
int tc=1;//cin >> tc;
while(tc--) _();
return 0;
}
