#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define MOD 1000000007
#define INF (1LL<<25)     //33554432
#define PI 3.14159265359
#define EPS 1e-12
//#define int ll

int mark[1000010];

signed main(void)
{
  set<int> num;
  int w, h, n;
  cin >> w >> h >> n;
  REP(i, n) {
    int s, k;
    cin >> s >> k;
    mark[s-1]++;
    num.insert(k-1);
  }

  int k = num.size(), ret = 0;
  REP(i, w) {
    if(mark[i]) {
      ret += h-mark[i];
    } else {
      ret += k;
    }
  }

  cout << ret << endl;
  return 0;
}