#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e9+7;
const ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ll,ii>
#define id pair<ll,vector<ll> >
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
ll n,m,k;
vector<set<ll> >adj,rev;
bool ok(ll l,ll r){
vector<set<ll> >X = rev;
set<ii>ex;
f(i,1,m+1){
set<ll>fkale;
for(auto x:X[i]){
if(x < l || x > r){
fkale.insert(x);
}
}
for(auto x:fkale){
X[i].erase(x);
}
ex.insert(ii(X[i].size(),i));
}
while(!ex.empty()){
ii f = (*ex.begin());
ex.erase(f);
if(f.F == 0){
return false;
}
ll go = (*X[f.S].begin());
for(auto x:adj[go]){
if(ex.count(ii(X[x].size(),x))){
ex.erase(ii(X[x].size(),x));
X[x].erase(go);
ex.insert(ii(X[x].size(),x));
}
}
}
return true;
}
int main(void){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin>>n>>m>>k;
adj.assign(n+5,set<ll>());
rev.assign(m+5,set<ll>());
f(i,0,k){
ll a,b;
cin>>a>>b;
adj[a].insert(b);
rev[b].insert(a);
}
ll ans = 0;
f(i,0,n){
ll l = i,r = n-1;
ll posa = n;
while(l <= r){
ll mid = (l+r)/2;
if(ok(i+1,mid+1)){
r = mid - 1;
posa = min(posa,mid);
}
else{
l = mid + 1;
}
}
ans += n - posa;
}
cout<<ans<<"\n";
}
