#include <cstdio>
#include <cstdint>
#include <vector>
#include <set>
#include <algorithm>

int main() {
  intmax_t W, H, N;
  scanf("%jd %jd %jd", &W, &H, &N);

  std::set<intmax_t> w, h;
  for (int i = 0; i < N; ++i) {
    int wi, hi;
    scanf("%d %d", &wi, &hi);
    w.insert(wi);
    h.insert(hi);
  }

  intmax_t w0 = w.size();
  intmax_t h0 = h.size();

  intmax_t res = 0;
  res += h0 * W;
  res += H * w0;
  res -= h0 * w0;
  res -= N;
  printf("%jd\n", res);
}