#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
using ll = long long;
const int maxn = 1e6 + 5;
int n,m,k;
vector<int> g[maxn];
int match[maxn]; //husbands
int seen[maxn]; //daughters
queue<int> need;
int L, R;
int cloc = 0;
bool dfs(int at) {
if (seen[at]==cloc) return false;
seen[at]=cloc;
for (int to: g[at]) {
if (L<=to && to<=R) {
if (match[to]==-1 || dfs(match[to])) {
match[to]=at;
return true;
}
}
}
return false;
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n>>m>>k;
for (int i=0; i<k; i++) {
int u,v;
cin>>u>>v;
--u; --v;
g[v].push_back(u);
}
for (int i=0; i<n; i++) {
match[i]=-1;
}
for (int i=0; i<m; i++) {
need.push(i);
}
ll ans = 0;
for (int l=0,r=0; l<n; l++) {
while (r<n) {
L=l; R=r;
while (need.size()) {
++cloc;
int at = need.front();
if (dfs(at)) {
need.pop();
} else {
break;
}
}
if (need.size()) {
++r;
} else {
break;
}
}
if (need.size()) {
break;
}
ans += n-r;
// get rid of husband l
if (match[l]>=0) {
need.push(match[l]);
match[l]=-1;
}
}
cout<<ans<<endl;
return 0;
}
