//#define TEST
#ifndef TEST
#include "aliens.h"
#endif
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define mp make_pair
typedef long long ll;
typedef pair<int, int> ii;
const int len = 1e5+5;
const ll inf = 1e15;
int n, m, k;
ii arr[len];
vector<ii> vec;
ll com[len];
pair<double, int> dp[len];
int check(double c){
for (int i = 1; i <= n; i++){
pair<double, int> ans = mp(inf, 0);
for (int j = 0; j < i; j++){
ll temp = (vec[i].se-vec[j+1].fi+1)*1LL*(vec[i].se-vec[j+1].fi+1) - com[j];
ans = min(ans, mp(dp[j].fi+temp, dp[j].se));
}
ans.fi += c;
ans.se += 1;
dp[i] = ans;
//printf("i = %d, ans = (%f, %d)\n", i, ans.fi, ans.se);
}
return dp[n].se;
}
ll bs(){
double l = 0, r = m*1LL*m, ans;
int it = 100;
while (it--){
double mid = (l+r)/2;
int cur = check(mid);
//printf("mid = %f, cur = %d\n", mid, cur);
if (cur <= k)
ans = mid, r = mid;
else
l = mid;
/*if (cur == k)
return mid;
if (cur < k)
r = mid;
else
l = mid;
*/
}
return ans;
}
ll take_photos(int N, int M, int K, vector<int> R, vector<int> C){
n = N, m = M, k = K;
for (int i = 0; i < n; i++){
arr[i] = mp(R[i]+1, C[i]+1);
if (arr[i].fi > arr[i].se)
swap(arr[i].fi, arr[i].se);
}
sort(arr, arr+n);
vec.pb(mp(1, 0));
for (int i = 0; i < n; i++){
while (vec.size() > 1 && vec.back().fi == arr[i].fi)
vec.pop_back();
if (arr[i].se > vec.back().se)
vec.pb(arr[i]);
}
n = vec.size()-1;
k = min(n, k);
for (int i = 0; i < n; i++){
if (vec[i].se < vec[i+1].fi)
com[i] = 0;
else
com[i] = (vec[i].se-vec[i+1].fi+1)*1LL*(vec[i].se-vec[i+1].fi+1);
}
//for (int i = 0; i <= n; i++)
// printf("%d %d\n", vec[i].fi, vec[i].se);
double c = bs();
int temp = check(c);
//printf("ans = %f\n", dp[n].fi - k*c);
return dp[n].fi - k*c;
}
#ifdef TEST
int main() {
printf("hello1\n");
int N, M, K;
assert(3 == scanf("%d %d %d", &N, &M, &K));
//printf("N = %d, M = %d, K = %d\n", N, M, K);
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
