#pragma GCC optimize ("O3")
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define ll long long
#define ld long double
#define all(a) a.begin(),a.end()
#define ull unsigned long long
#define endl '\n'
#define y1 yaumru
#define ios ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define iter vector<int>::iterator
#define int long long
using namespace std;
using namespace __gnu_pbds;
template<class T>
using ordered_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
template<class T>
using ordered_multiset=tree<T,null_type,less_equal<T>,rb_tree_tag,tree_order_statistics_node_update>;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rnd1(chrono::steady_clock::now().time_since_epoch().count());
//find_by_order
//order_of_key
const int N=30000+7;
const int inf=1e18+5;
const int mod=1e9+7;
const ld eps=1e-9;
vector<int>g[N];
bool used[N];
int mt[N];
int n,m;
bool used1[N];
bool try_kuhn (int v,int l,int r) {
if (used[v]) return false;
used[v] = true;
for (size_t i=0; i<g[v].size(); ++i) {
int to = g[v][i];
if (to<l || to>r)continue;
if (mt[to] == -1 || try_kuhn (mt[to],l,r)) {
mt[to] = v;
return true;
}
}
return false;
}
bool check(int l,int r)
{
fill(mt,mt+n+1,-1);
fill(used1,used1+m+1,false);
for (int i=1;i<=m;++i){
for (int j=0;j<g[i].size();++j){
int to=g[i][j];
if (to>=l && to<=r){
if (mt[to]==-1){
mt[to]=i;
used1[i]=true;
break;
}
}
}
}
for (int i=1;i<=m;++i){
if (used1[i])continue;
fill(used,used+m+1,false);
try_kuhn(i,l,r);
}
int ans=0;
for (int i=1;i<=n;++i){
if (mt[i]!=-1)++ans;
}
if (ans!=m)return false;
return true;
}
main ()
{
ios;
int k;
cin>>n>>m>>k;
for (int i=1;i<=k;++i){
int x,y;
cin>>x>>y;
swap(x,y);
g[x].pb(y);
}
int ans=0;
int r=1;
for (int i=1;i<=n;++i){
while(r<=n && !check(i,r))++r;
ans+=n-r+1;
}
cout<<ans<<endl;
}
