#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, w, h, n, x, y, left, right, up, down;
  cin >> w >> h >> n;
  left = 0;
  right = w;
  down = 0;
  up = h;
  for (int i = 1; i <= n; i++) {
    cin >> x >> y >> a;
    if (a == 1) left = max(left, x);
    if (a == 2) right = min(right, x);
    if (a == 3) down = max(down, y);
    if (a == 4) up = min(up, y);
  }
  if (left > right || down > up)
    cout << 0;
  else
    cout << (right - left) * (up - down);
  return 0;
}
