#include <cstdio>
#include <algorithm>
#include <vector>
#include <map>
using namespace std;
const int NMAX = 2e5;
int n,m;
pair<int,int> v[NMAX + 5];
vector<int> vals;
map<int,int> stuff;
pair<long long,int> aib[NMAX + 5];
void update(int pos,pair<int,int> val) {
pos = (int)vals.size() - pos + 1;///for enhanced binary searche
for(; pos <= (int)vals.size(); pos += (-pos) & pos) {
aib[pos].first += val.first;
aib[pos].second += val.second;
}
}
long long get_best_sum(int cnt) {
pair<long long,int> lst = {0,0};
int pos = 0;
for(int h = 1 << 18; h; h >>= 1) {
if(pos + h <= (int)vals.size() && lst.second + aib[pos + h].second < cnt) {
pos += h;
lst.first += aib[pos].first;
lst.second += aib[pos].second;
}
}
lst.first += 1LL * (cnt - lst.second) * vals[(int)vals.size() - pos - 1];
return lst.first;
}
int ins_cnt;
void add(pair<int,int> a) {
ins_cnt++;
stuff[a.second]++;
update(lower_bound(vals.begin(),vals.end(),a.first) - vals.begin() + 1, {a.first,1});
}
void rem(pair<int,int> a) {
ins_cnt--;
stuff[a.second]--;
if(stuff[a.second] == 0){
stuff.erase(a.second);
}
update(lower_bound(vals.begin(),vals.end(),a.first) - vals.begin() + 1, {-a.first,-1});
}
long long query(int cnt) {
if(cnt > ins_cnt) {
return 0;
}
long long ans = -stuff.rbegin()->first + stuff.begin()->first + get_best_sum(cnt);
return ans;
}
int st = 1,dr = 0;
long long calc(int l,int r) {
while(st > l) {
add(v[--st]);
}
while(dr < r) {
add(v[++dr]);
}
while(st < l) {
rem(v[st++]);
}
while(dr > r) {
rem(v[dr--]);
}
return query(m);
}
long long solve(int st,int dr,int lo,int hi) {
if(st > dr) {
return 0;
}
int mid = (st + dr) / 2;
pair<long long,int> bst = {0,0};
for(int i = max(lo,mid); i <= hi; i++) {
bst = max(bst, {calc(mid,i),i});
}
if(st == dr) {
return bst.first;
}
return max(max(solve(st,mid - 1,lo,bst.second),solve(mid + 1,dr,bst.second,hi)),bst.first);
}
int main() {
scanf("%d %d",&n,&m);
for(int i = 1; i <= n; i++) {
scanf("%d %d",&v[i].first,&v[i].second);
v[i].second *= 2;
vals.push_back(v[i].first);
}
sort(vals.begin(),vals.end());
vals.resize(unique(vals.begin(),vals.end()) - vals.begin());
sort(v + 1,v + 1 + n,[&]
(const pair<int,int> &a,const pair<int,int> &b) {
if(a.second != b.second) {
return a.second < b.second;
}
return a.first < b.first;
});
printf("%lld\n",solve(1,n,1,n));
return 0;
}
