#include<bits/stdc++.h>
using namespace std;
#define task "a"
#define se second
#define fi first
#define ll long long
#define ii pair<ll, ll>
const long mxN = 2e5 + 7;
const ll inf = 1e18;
bool dd[mxN];
int n, k;
ll sum;
ii a[mxN], tree[mxN * 4][2];
set<int> s;
priority_queue<ii, vector<ii>, greater<ii>> pq;
void Upd(int vt, bool tt, int j = 1, int l = 1, int r = n)
{
if (l > vt || vt > r)
return;
if (l == r)
{
tree[j][1] = {a[l].se * tt, l};
tree[j][0] = {(a[l].se + a[l].fi) * tt, l};
return;
}
int mid = (l + r) / 2;
Upd(vt, tt, j * 2, l, mid);
Upd(vt, tt, j * 2 + 1, mid + 1, r);
tree[j][0] = max(tree[j * 2][0], tree[j * 2 + 1][0]);
tree[j][1] = max(tree[j * 2][1], tree[j * 2 + 1][1]);
}
ii Get(int vt, int j = 1, int l = 1, int r = n)
{
if (r < vt)
return tree[j][0];
if (l >= vt)
{
if (tree[j][1].fi)
return {tree[j][1].fi + a[vt].fi * 2, tree[j][1].se};
else
return tree[j][1];
}
int mid = (l + r) / 2;
return max(Get(vt, j * 2, l, mid), Get(vt, j * 2 + 1, mid + 1, r));
}
void Add(int j)
{
dd[j] = 1;
pq.push({a[j].se, j});
Upd(j, 0);
s.insert(j);
sum += a[j].se;
}
void Rem(int j)
{
dd[j] = 0;
Upd(j, 1);
s.erase(j);
sum -= a[j].se;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
//freopen(task".INP", "r", stdin);
//freopen(task".OUT", "w", stdout);
cin >> n >> k;
for (int i = 1; i <= n; i++)
cin >> a[i].se >> a[i].fi;
sort(a + 1, a + n + 1);
for (int i = 1; i < k; i++)
Add(i);
ll ans = -inf;
for (int i = k; i <= n; i++)
{
Add(i);
ans = max(ans, sum - (a[i].fi - a[*s.begin()].fi) * 2);
while (pq.size())
{
int j = pq.top().se;
pq.pop();
if (!dd[j])
continue;
Rem(j);
break;
}
while (1)
{
int nxt = *s.upper_bound(*s.begin());
ii j = Get(nxt);
if (j.fi > a[*s.begin()].se + a[*s.begin()].fi * 2)
{
Rem(*s.begin());
Add(j.se);
}
else
break;
}
}
cout << ans;
}
