#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
const int MAXN = 300100;
int seg[MAXN*4];
int x[MAXN], y[MAXN], child[MAXN], L[MAXN], R[MAXN], vis[MAXN];
priority_queue<pair<ll,int>> pq;
ll fuck[MAXN];
void build_rmq(int node, int s, int e){
if(s==e){
seg[node] = s; return;
}
int m = s+e>>1;
build_rmq(2*node, s,m); build_rmq(2*node+1,m+1,e);
int a = seg[2*node], b = seg[2*node+1];
seg[node] = (y[a]>y[b]) ? b : a;
}
int query(int node, int s, int e, int l, int r){
if(r<s || l>e) return -1;
if(l<=s && e<=r) return seg[node];
int m = s+e>>1;
int a = query(2*node,s,m,l,r), b = query(2*node+1,m+1,e,l,r);
if(a==-1) return b; if(b==-1) return a;
return y[a]>y[b] ? b : a;
}
int n;
int pv;
void build(int node, int s, int e, int h){
int idx = query(1,1,n,s,e);
//cerr << idx << endl;
ll val = (ll)(x[e]-x[s-1])*(y[idx]-h);
//cerr << x[s-1] << endl;
L[node] = -1, R[node] = -1;
if(s<=idx-1){
pv++;
L[node] = pv;
build(pv,s,idx-1,y[idx]);
}
if(idx+1<=e){
pv++;
R[node] = pv;
build(pv,idx+1,e,y[idx]);
}
ll l = (L[node]!=-1 ? fuck[L[node]] : 0), r = (R[node]!=-1 ? fuck[R[node]] : 0);
fuck[node] = val + max(l,r);
if(l>r) child[node] = L[node];
else if(r>l) child[node] = R[node];
else{
if(r==0) child[node] = -1;
else child[node] = L[node];
}
pq.push({fuck[node],node});
}
int32_t main(void){
ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
cin >> n; n = (n-1)>>1;
cin >> x[0] >> y[0];
for(int i=1; i<=n; i++){
cin >> x[i] >> y[i]; cin >> x[i] >> y[i];
}
cin >> x[0] >> y[0];
x[0] = 0, y[0] = 0;
build_rmq(1,1,n);
build(0,1,n,0); //cerr << "fuck" << endl;
int k; cin >> k;
ll ans = 0; int cnt = 0;
while(cnt<k && !pq.empty()){
auto [val, i] = pq.top(); pq.pop();
//cerr << val << " " << i << endl;
if(vis[i]) continue; ans += val;
//cerr << i << " " << val << endl;
while(i!=-1) {
vis[i] = 1; i = child[i];
}
cnt++;
}
cout << ans;
}
