#include <bits/stdc++.h>
using namespace std;
#ifndef LOCAL
#include "aliens.h"
#endif
long long take_photos(int n, int m, int k, vector<int> r, vector<int> c) {
using pii = pair<int, int>;
vector<pii> p(n);
vector<vector<long long>> f(k + 1, vector<long long>(n + 1, 1e15));
for (int i = 0; i < n; ++i) p[i] = {r[i], c[i]};
if (n <= 50 && m <= 100 && k == n) {
vector<vector<bool>> mk(m, vector<bool>(m));
for (int i = 0; i < n; ++i) {
auto [x, y] = p[i];
if (x > y) swap(x, y);
for (int i = x; i <= y; ++i) {
for (int j = x; j <= y; ++j) mk[i][j] = true;
}
}
int answer = 0;
for (int i = 0; i < m; ++i)
for (int j = 0; j < m; ++j) answer += mk[i][j];
return answer;
}
auto dis = [&](pii a) { return abs(a.first - a.second) + 1; };
sort(p.begin(), p.end(), [&](const auto& a, const auto& b) {
return make_pair(a.first, dis(a)) < make_pair(b.first, dis(b));
});
return 0;
}
#ifdef LOCAL
int32_t main() {
cin.tie(0)->sync_with_stdio(0);
int n, m, k; cin >> n >> m >> k;
vector<int> r(n), c(n);
for (int i = 0; i < n; ++i) cin >> r[i] >> c[i];
cout << take_photos(n, m, k, r, c) << "\n";
}
#endif
