#include <bits/stdc++.h>
#define int long long
#define p_be second
#define p_ta first
using namespace std;
using idata = vector<int>;
using t_perle = pair<int, int>;
using t_perles = vector<t_perle>;
signed main () {
int N, M;
cin >> N >> M;
t_perles perles;
set<int> beauty_set;
for (int i = 0; i < N; i ++) {
int b, t;
cin >> b >> t;
beauty_set.insert(b);
perles.push_back({ t, b });
}
idata beauty_unique;
for (int u : beauty_set) beauty_unique.push_back(u);
sort(perles.begin(), perles.end());
idata beauty;
for (const auto &perle : perles)
beauty.push_back(perle.p_be);
int max_result = -1e18;
for (int left = 0; left < N; left ++) {
priority_queue<int> vs; int sum = 0;
for (int i = left; i <= left + M - 1; i ++) {
sum += beauty[i];
vs.push(- beauty[i]);
}
for (int right = left + M - 1; right < N; right ++) {
int low = - vs.top();
if (low < beauty[right] && right != left + M - 1) {
vs.pop();
sum -= low;
sum += beauty[right];
vs.push(-beauty[right]);
}
int result = 2 * (perles[left].p_ta - perles[right].p_ta) + sum;
max_result = max(max_result, result);
}
}
cout << max_result << endl;
}
