#include <bits/stdc++.h>
using namespace std;
using pii = pair<int, int>;
struct Node {
int c; long long s;
int lc, rc;
};
const long long INF = 1LL * 1e18;
const Node emp = {0, 0, -1, -1};
struct PST {
vector<int> root;
vector<Node> T;
void init(int idx, int s, int e) {
T[idx] = emp;
if(s == e) return;
T[idx].lc = idx*2;
T[idx].rc = idx*2+1;
int m = s+e >> 1;
init(idx*2, s, m);
init(idx*2+1, m+1, e);
}
long long get(int pid, int nid, int s, int e, int k) {
//printf("pseg get: pid: %d, nid: %d, s: %d, e: %d, k: %d\n", pid, nid, s, e, k);
int cnt = T[nid].c - T[pid].c;
if(cnt == k) return T[nid].s - T[pid].s;
if(cnt < k) return -INF;
int plc = T[pid].lc, nlc = T[nid].lc, prc = T[pid].rc, nrc = T[nid].rc, m = s+e >> 1;
int rcnt = T[nrc].c - T[prc].c;
if(rcnt >= k) return get(prc, nrc, m+1, e, k);
return T[nrc].s - T[prc].s + get(plc, nlc, s, m, k - rcnt);
}
long long ksum(int l, int r, int s, int e, int k) {
return get(root[l], root[r], s, e, k);
}
void upd(int pid, int nid, int s, int e, int p, int v) {
//printf("pseg upd: pid: %d nid: %d s: %d e: %d p: %d v: %d\n", pid, nid, s, e, p, v);
if(s == e) {
++T[nid].c;
T[nid].s += v;
return;
}
int m = s+e >> 1;
if(p <= m) {
T[nid].lc = T.size();
T.push_back(T[T[pid].lc]);
upd(T[pid].lc, T[nid].lc, s, m, p, v);
T[nid].rc = T[pid].rc;
}
else {
T[nid].lc = T[pid].lc;
T[nid].rc = T.size();
T.push_back(T[T[pid].rc]);
upd(T[pid].rc, T[nid].rc, m+1, e, p, v);
}
int LC = T[nid].lc, RC = T[nid].rc;
T[nid].c = T[LC].c + T[RC].c;
T[nid].s = T[LC].s + T[RC].s;
}
void update(int s, int e, int p, int v) {
int pid = root.back(), nid = T.size();
root.push_back(nid);
T.push_back(T[pid]);
upd(pid, nid, s, e, p, v);
}
void initalization(int sz) {
root.push_back(1);
T.resize(4*sz);
init(1, 1, sz);
}
};
PST pseg;
long long ans = -INF;
int N, M, V[200009], C[200009], ord[200009];
vector<int> S = {0};
void dnc(int s, int e, int l, int r) {
if(e < s || r < l) return;
int m = s+e >> 1;
int st = max(m + M - 1, l), en = r, mxi = r;
int L = S[m];
long long mx = -INF;
for(int i=st; i<=en; i++) {
int R = S[i];
long long tmp = - 2LL * (C[R] - C[L]) + V[L] + V[R] + pseg.ksum(m, i-1, 1, N, M-2);
if(mx <= tmp) mxi = i, mx = tmp;
ans = max(ans, tmp);
}
dnc(s, m-1, l, mxi);
dnc(m+1, e, mxi, r);
}
int main() {
vector<pii> VS;
scanf("%d%d",&N,&M);
for(int i=1; i<=N; i++) {
scanf("%d%d",&V[i],&C[i]);
VS.push_back({V[i], i});
S.push_back(i);
} C[0] = -1e9;
sort(S.begin(), S.end(), [&](int P, int Q) {return C[P] < C[Q];});
sort(VS.begin(), VS.end());
for(int i=1; i<=N; i++) ord[VS[i-1].second] = i;
pseg.initalization(N);
for(int i=1; i<=N; i++) {
int it = S[i];
pseg.update(1, N, ord[it], V[it]);
}
dnc(1, N, 1, N);
printf("%lld", ans);
return 0;
}
