#include <bits/stdc++.h>
#define tt cin.tie(0), cout.tie(0), ios_base::sync_with_stdio(0)
#define fo freopen((NAME+".INP").c_str(), "r", stdin), freopen((NAME+".OUT").c_str(), "w", stdout)
#define ll long long
#define ull unsigned long long
#define i128 __int128
#define db long double
#define sz(a) ((int)(a).size())
#define pb emplace_back
#define pf emplace_front
#define pob pop_back
#define pof pop_front
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define ins emplace
#define mp make_pair
using namespace std;
const int MOD = 1e9+7, MAXN = 2e5+5;
const string NAME = "";
int n,m,L,R;
ll rs=0,sum=0,preMAX[MAXN];
pair<int,int> p[MAXN];
multiset<int, greater<int>> ms1,ms2;
void add(int x){
if(sz(ms1)<m) ms1.ins(x), sum+=x;
else if(*ms1.rbegin()<x) ms2.ins(*ms1.rbegin()), sum-=*ms1.rbegin(), ms1.erase(prev(ms1.end())), ms1.ins(x), sum+=x;
else ms2.ins(x);
}
void rem(int x){
if(!ms2.empty()&&*ms2.begin()>=x) ms2.erase(ms2.find(x));
else{
ms1.erase(ms1.find(x)), sum-=x;
if(!ms2.empty()) sum+=*ms2.begin(), ms1.ins(*ms2.begin()), ms2.erase(ms2.begin());
}
}
void dnc(int l, int r, int optl, int optr){
if(l>r||optl>optr) return;
int mid=(l+r)>>1;
while(R>mid-1) rem(p[R--].se);
while(R<mid-1) add(p[++R].se);
while(L>min(mid-m,optr)) add(p[--L].se);
while(L<min(mid-m,optr)) rem(p[L++].se);
pair<ll,int> opt={-1e18,0};
for(int i = min(optr,mid-m); i>=optl; --i){
if(L>i) add(p[--L].se);
opt=max(opt,mp(preMAX[i-1]-2ll*p[mid].fi+p[mid].se+sum,i));
}
rs=max(rs,opt.fi);
dnc(l,mid-1,optl,opt.se);
dnc(mid+1,r,opt.se,optr);
}
int main()
{
tt;
if(fopen((NAME + ".INP").c_str(), "r")) fo;
cin >> n >> m;
for(int i = 1; i<=n; ++i)
cin >> p[i].se >> p[i].fi;
sort(p+1,p+n+1);
preMAX[1]=p[1].se+2ll*p[1].fi;
for(int i = 2; i<=n; ++i)
preMAX[i]=max(preMAX[i-1],p[i].se+2ll*p[i].fi);
m-=2, L=2, R=n-m;
for(int i = 2; i<=n-m; ++i)
add(p[i].se);
dnc(m+2,n,2,n-m);
cout << rs;
}
