#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 << 30)-1;
ll sum = 0;
int cnt = 0;
node* left = NULL;
node* right = NULL;
void gen_sons()
{
if(left == NULL)
{
left = new node;
left -> l = l;
left -> r = (l+r)/2;
}
if(right == NULL)
{
right = new node;
right -> l = (l+r)/2+1;
right -> r = r;
}
}
void add(ll x, node* prev)
{
if(prev != NULL)
{
sum = prev->sum;
cnt = prev->cnt;
}
sum += x;
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,(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,(prev != NULL ? prev -> right : NULL));
}
}
ll get_sum(node* prev, int k)
{
if(l == r)
{
return (ll)l * min(k,cnt - prev -> cnt);
}
prev-> gen_sons();
gen_sons();
int r_cnt = right -> cnt - prev -> right -> cnt;
if(r_cnt >= k) return right->get_sum(prev->right,k);
return left->get_sum(prev->left,k-r_cnt) + right -> sum - prev->right->sum;
}
};
ll V[200001];
ll C[200001];
vector<node> nodes;
ll get_sum(int l, int r)
{
return nodes[r+1].get_sum(&nodes[l],m);
}
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));
rep(i,n)
{
V[i] = v_sort[i].ss;
C[i] = v_sort[i].ff;
}
node xd;
nodes.pb(xd);
rep(i,n)
{
node new_node;
new_node.add(V[i],&nodes.back());
nodes.pb(new_node);
}
ll ans = -1e18;
rep(l,n-m+1)
{
rep2(r,l+m-1,n-1)
{
ans = max(ans,get_sum(l,r) - (C[r]-C[l])*2);
}
}
cout << ans << "\n";
}
