#include <iostream>
#include <cstring>
using namespace std;

typedef long long ll;

ll w, h, n;
ll s[100], k[100];
bool flgS[1000002], flgK[1000002];

int main(){
  while(cin >> w >> h >> n){
    memset(flgS, 0, sizeof(flgS));
    memset(flgK, 0, sizeof(flgK));

    ll kcnt = 0;

    for(ll i = 0; i < n; i++){
      cin >> s[i] >> k[i];

      if(!flgK[k[i]]) kcnt++;
      flgS[s[i]] = true;
      flgK[k[i]] = true;
    }

    ll ans = -n;

    for(ll i = 1; i <= w; i++){
      if(flgS[i]){
        ans += h;
      }
      else{
        ans += kcnt;
      }
    }

    cout << ans << endl;
  }
}