#include <bits/stdc++.h>
using namespace std;
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
#define ll long long
#define ld long double
#define all(a) (a).begin(), (a).end()
#define sui cout.tie(NULL); cin.tie(NULL); ios_base::sync_with_stdio(false)
const int MAX_N = 1e5 + 5;
const int MOD = 1e9 + 7;
const ll INF = 1e18;
const ld EPS = 1e-9;
const int LOG = 30;
void solve() {
int n, m;
cin >> n >> m;
vector<pair<int, int>> vs;
for (int i = 0; i < n; i++)
{
int a, b;
cin >> a >> b;
vs.push_back(make_pair(b, a));
}
sort(all(vs));
ll ans = -INF;
for (int i = 0; i < n; i++) for (int j = i; j < n; j++)
{
if (j - i + 1 < m) continue;
vector<int> al;
for (int k = i + 1; k < j; k++) al.push_back(vs[k].second);
sort(all(al), greater<int>());
ll sum = 0;
for (int i = 0; i < m - 2; i++) sum += al[i];
ans = max(ans, sum + vs[i].second + vs[j].second - 2 * (vs[j].first - vs[i].first));
}
cout << ans << "\n";
}
int main() {
sui;
int tc = 1;
//cin >> tc;
for (int t = 1; t <= tc; t++) {
solve();
}
}
