#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
int n,m;
struct node
{
int l = 0;
int r = (1 << 18)-1;
ll sum = 0;
int cnt = 0;
node* left = NULL;
node* right = NULL;
void add(int x, ll val, node* prev)
{
if(prev != NULL)
{
sum = prev->sum;
cnt = prev->cnt;
}
sum += val;
cnt++;
if(l == r)
{
return;
}
if(x <= (l+r)/2)
{
if(prev != NULL) right = prev -> right;
left = new node;
left -> l = l;
left -> r = (l+r)/2;
left -> add(x,val,(prev != NULL ? prev -> left : NULL));
}
else
{
if(prev != NULL) left = prev -> left;
right = new node;
right -> l = (l+r)/2+1;
right -> r = r;
right -> add(x,val,(prev != NULL ? prev -> right : NULL));
}
}
ll get_sum(node* prev, int k)
{
if(l == r)
{
return (ll)(sum/cnt) * min(k,cnt - (prev != NULL ? prev -> cnt : 0));
}
int r_cnt = (right != NULL ? right -> cnt : 0) - (prev != NULL && prev -> right != NULL ? prev -> right -> cnt : 0);
if(r_cnt >= k) return (right != NULL ? right->get_sum((prev != NULL && prev -> right != NULL ? prev->right : NULL),k) : 0);
return (left != NULL ? left->get_sum((prev != NULL && prev->left != NULL ? prev->left : NULL),k-r_cnt) : 0) + (right != NULL ? right -> sum : 0) - (prev != NULL && prev -> right != NULL ? prev -> right -> sum : 0);
}
};
ll V[200001];
ll C[200001];
vector<node> nodes;
ll ans = -1e18;
ll get_sum(int l, int r)
{
if(r-l+1 < m) return -1e18;
return nodes[r+1].get_sum(&nodes[l],m) - (C[r]-C[l])*2;
}
void solve(int l, int r, int l2, int r2)
{
if(l > r) return;
int mid = (l+r)/2;
pll best = {-1e18,1};
rep2(i,l2,r2)
{
if(i <= mid)
{
best = max(best,{get_sum(i,mid),i});
}
}
ans = max(ans,best.ff);
solve(l,mid-1,l2,best.ss);
solve(mid+1,r,best.ss,r2);
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//random_start();
cin >> n >> m;
vector<pll> v_sort;
rep(i,n)
{
ll v,c;
cin >> v >> c;
v_sort.pb({c,v});
}
sort(all(v_sort));
map<ll,int> poz;
rep(i,n)
{
V[i] = v_sort[i].ss;
C[i] = v_sort[i].ff;
poz[V[i]] = 0;
}
int cur = 0;
forall(it,poz)
{
poz[it.ff] = cur++;
}
node xd;
nodes.pb(xd);
rep(i,n)
{
node new_node;
new_node.add(poz[V[i]],V[i],&nodes.back());
nodes.pb(new_node);
}
solve(m-1,n-1,0,n-1);
cout << ans;
}
