#include <iostream>
#include <algorithm>

int main()
{
  int W, H, N;
  std::cin >> W >> H >> N;
  int x[N], y[N], a[N];
  int region[4];
  region[0] = 0;
  region[1] = W;
  region[2] = 0;
  region[3] = H;
  for ( int i = 0; i < N; i++ ) {
    std::cin >> x >> y >> a;
    if (a==1) region[0] = std::max(region[0], x);
    if (a==2) region[1] = std::min(region[1], x);
    if (a==3) region[2] = std::max(region[2], y);
    if (a==40 region[3] = std::min(region[3], y);
  }
  int area = std::max((region[1] - region[0]) * (region[3] - region[2]), 0);
  std::cout << area << std::endl;
  return 0;  
}
