#define JUDGE
#ifndef JUDGE
#include "aliens.h"
#endif // JUDGE
#include "bits/stdc++.h"
using namespace std;
typedef pair <int, int> pii;
vector <pii> range;
bool comp(pii a, pii b) {
if(a.first == b.first) {
return a.second > b.second;
} else {
return a.first < b.first;
}
}
long long count(int x, int y) {
if(x <= y) return 1LL * (y - x + 1) * (y - x + 1);
return 0;
}
long long dp[2][4005];
long long take_photos(int n, int m, int k, std::vector<int> r, std::vector<int> c) {
set <pii> all;
for(int i = 0; i < n; i++) {
int x = min(r[i], c[i]);
int y = max(r[i], c[i]);
all.insert(make_pair(x, y));
}
const long long INF = 1e16;
vector <pii> aux (all.begin(), all.end());
for(auto i : aux) {
bool good = true;
for(auto j : aux) {
if(i == j) continue;
if(j.first <= i.first && i.second <= j.second) {
good = false;
}
}
if(good) range.push_back(i);
}
range.push_back(make_pair(-1, -1));
sort(range.begin(), range.end());
int sz = range.size() - 1;
memset(dp, 0, sizeof dp);
for(int i = 1; i <= sz; i++) {
dp[0][i] = INF;
}
int ro = 0;
for(int i = 1; i <= k; i++) {
ro ^= 1;
for(int j = 1; j <= sz; j++) {
dp[ro][j] = INF;
for(int l = 1; l <= j; l++) {
dp[ro][j] = min(dp[ro][j], dp[ro ^ 1][l - 1] + count(range[l].first, range[j].second) - count(range[l].first, range[l-1].second));
}
}
}
return dp[ro][sz];
}
#ifndef JUDGE
int main() {
int n, m, k;
assert(3 == scanf("%d %d %d", &n, &m, &k));
std::vector<int> r(n), c(n);
for (int i = 0; i < n; i++) {
assert(2 == scanf("%d %d", &r[i], &c[i]));
}
long long ans = take_photos(n, m, k, r, c);
printf("%lld\n", ans);
return 0;
}
#endif // JUDGE
