#include <stdio.h>
#include <map>
#include <set>
#include <vector>
#include <queue>
#include <algorithm>
#define LL long long
#define pii pair<int, int>
#define ff first
#define ss second
using namespace std;
vector<int> X, Y;
struct Line{
int sx, ex, y;
Line(int sx, int ex, int y) : sx(sx), ex(ex), y(y) {}
bool operator < (const Line &l) const {
if(y != l.y) return y > l.y;
return sx > l.sx;
}
};
struct Plane{
int sx, ex, sy, ey;
}P[150021];
map<pii, int> mp;
set<int> st1, st2;
vector<int> edge[150021];
int par[150021];
priority_queue<LL> pq;
LL dfs(int v){
LL mx = 0;
for(int u : edge[v]){
LL res = dfs(u);
if(mx < res){
if(mx) pq.push(mx);
mx = res;
}
else pq.push(res);
}
return mx+(LL)(P[v].sx-P[v].ex)*(P[v].sy-P[v].ey);
}
int main(){
int n, k;
scanf("%d", &n);
for(int i = 1; i <= n; i++){
int x, y; scanf("%d %d", &x, &y);
X.push_back(x);
Y.push_back(y);
}
scanf("%d", &k);
X.erase(unique(X.begin(), X.end()), X.end());
Y.erase(unique(Y.begin(), Y.end()), Y.end());
//for(int x : X) printf("%d ", x); printf("\n");
//for(int y : Y) printf("%d ", y); printf("\n");
vector<Line> L;
for(int i = 1; i < X.size(); i++) L.push_back(Line(X[i-1], X[i], Y[i]));
//for(Line l : L) printf("%d %d %d\n", l.sx, l.ex, l.y); printf("\n");
sort(L.begin(), L.end());
//for(Line l : L) printf("%d %d %d\n", l.sx, l.ex, l.y); printf("\n");
int piv = 0;
mp[{X.front(), X.back()}] = ++piv;
P[piv].sx = X.front();
P[piv].ex = X.back();
P[piv].sy = 0;
st1.insert(X.front());
st1.insert(X.back());
while(!L.empty()){
int y = L.back().y;
vector<int> vc;
set<int> st;
while(!L.empty() && L.back().y == y){
Line l = L.back(); L.pop_back();
set<int>::iterator it2 = st1.lower_bound(l.ex);
set<int>::iterator it1 = it2; it1--;
P[mp[{*it1, *it2}]].ey = y;
if(st.find(*it1) == st.end()) st.insert(*it1);
if(st.find(*it2) == st.end()) st.insert(*it2);
if(st2.find(l.sx) == st2.end()) st2.insert(l.sx);
else st2.erase(l.sx);
if(st2.find(l.ex) == st2.end()) st2.insert(l.ex);
else st2.erase(l.ex);
vc.push_back(l.sx);
vc.push_back(l.ex);
}
for(int x : st){
if(st2.find(x) == st2.end()) st2.insert(x);
else st2.erase(x);
}
st.clear();
for(set<int>::iterator it21 = st2.begin(); it21 != st2.end(); it21++, it21++){
set<int>::iterator it22 = it21; it22++;
set<int>::iterator it12 = st1.lower_bound(*it22);
set<int>::iterator it11 = it12; it11--;
mp[{*it21, *it22}] = ++piv;
P[piv].sx = *it21;
P[piv].ex = *it22;
P[piv].sy = y;
int p = mp[{*it11, *it12}];
edge[p].push_back(piv);
par[piv] = p;
}
for(int x : vc){
if(st1.find(x) == st1.end()) st1.insert(x);
else st1.erase(x);
}
st2.clear();
vc.clear();
}
/*
for(int i = 1; i <= piv; i++){
printf("%d : ", i); for(int u : edge[i]) printf("%d ", u); printf(": ");
printf("%d %d %d %d\n", P[i].sx, P[i].ex, P[i].sy, P[i].ey);
}
printf("\n");
*/
pq.push(dfs(1));
LL sum = 0;
for(;!pq.empty() && k--; pq.pop()) sum += pq.top();
printf("%lld", sum);
return 0;
}
