/**
____ ____ ____ ____ ____ ____
||l |||e |||i |||n |||a |||d ||
||__|||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|/__\|
**/
#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
typedef long long ll;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
}
const int maxn = 2e5 + 10;
struct element
{
ll v, s, idx;
element(ll _v = 0, ll _s = 0, ll _idx = 0)
{
v = _v;
s = _s;
idx = _idx;
}
}e[maxn];
int n, m;
void input()
{
cin >> n >> m;
for (int i = 1; i <= n; i ++)
{
cin >> e[i].v >> e[i].s;
e[i].s *= 2;
e[i].idx = i;
}
}
bool cmp_second(element e1, element e2)
{
return e1.s < e2.s;
}
ll inf = 1e18;
ll result;
ll dp[maxn];
ll cost(int left, int right)
{
//cout << "cost " << left << " " << right << endl;
vector < ll > values;
for (int i = left; i <= right; i ++)
values.push_back(e[i].v);
sort(values.begin(), values.end());
ll res = 0;
for (int i = (int)(values.size()) - 1; i >= (int)(values.size()) - m; i --)
res += values[i];
//exit(0);
return res;
}
void divide(int l, int r, int optl, int optr)
{
if (l > r)
return;
///cout << l << " " << r << " " << optl << " " << optr << endl;
int mid = max(optl + m - 1, (l + r) / 2), opt = -1;
if (mid > r)
return;
for (int i = optl; i <= min(optr, mid); i ++)
{
///cout << "check " << mid << " " << i << endl;
if (mid - i + 1 >= m)
{
ll sum = - e[mid].s + e[i].s + cost(i, mid);
///cout << "alive " << " " << sum << endl;
if (sum > dp[mid])
{
dp[mid ] = sum;
opt = i;
}
}
}
//cout << "pos " << mid << " " << opt << endl;
divide(l, mid - 1, optl, opt);
divide(mid + 1, r, opt, optr);
}
void print()
{
ll best = -inf;
for (int i = 1; i <= n; i ++)
best = max(best, dp[i]);
cout << best << endl;
}
void solve()
{
input();
sort(e + 1, e + n + 1, cmp_second);
for (int i = 1; i <= n; i ++)
dp[i] = -inf;
divide(1, n, 1, n);
print();
}
int main()
{
solve();
return 0;
}
