/// wa
#pragma GCC optimize("O3")
//#pragma comment(linker, "/STACK:36777216")
#include<bits/stdc++.h>
#define x first
#define y second
#define pb push_back
#define sz(x) (int) x.size()
#define all(z) (z).begin(), (z).end()
using namespace std;
using ll = long long;
using pii = pair<int, int>;
const int MOD = 1e9 + 7;
const int INF = 1e9 + 1e2;
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void fin() {
#ifdef AM
freopen(".in", "r", stdin);
#endif
}
const bool flag = 0;
const int N = 2e3+10;
const int M = 3e4+10;
int was[N];
int mt[M], p[M], tmp;
vector<int> adj[N];
bool dfs(int x) {
if (was[x] == tmp) return 0;
was[x] = tmp;
for (int to : adj[x]) {
if (mt[to] == -1) {
mt[to] = x;
p[x] = to;
return 1;
}
}
for (int to : adj[x]) {
if (dfs(to)) {
mt[to] = x;
p[x] = to;
return 1;
}
}
return 0;
}
void ma1n() {
int n, m, k;
cin >> n >> m >> k;
vector<vector<int>> g(n);
for (int u, v; k--;) {
cin >> u >> v;
u--, v--;
g[u].pb(v);
}
int r = 0;
ll ans = 0;
memset(mt, -1, sizeof(mt));
int prev = -1;
for (int l = 0; l < n; ++l) {
bool ok = 0;
while (r < n && !ok) {
for (int to : g[r]) {
adj[to].pb(r);
}
fill(p, p+m, -1);
for (int i = 0; i < m; ++i) {
tmp++;
dfs(i);
}
ok = 1;
for (int i = 0; i < m; ++i) {
if (~p[i]) {
mt[p[i]] = -1;
} else {
ok = 0;
}
}
r++;
}
for (int to : g[l]) {
adj[to].erase(find(all(adj[to]), l));
}
if (ok) {
ans += (l-prev) * 1ll * (n-r+1);
prev = l;
}
}
cout << ans;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(nullptr), fin();
int ts = 1;
if (flag) {
cin >> ts;
}
while (ts--) {
ma1n();
}
return 0;
}
