#include <stdio.h>
#include <stdlib.h>
int cmp(const void* a, const void* b)
{
  return (*(int*)a - *(int*)b);
}
int main()
{
  int i;
  int W;
  int H;
  int N;
  int *S;
  int *K;
  scanf("%d", &W);
  scanf("%d", &H);
  scanf("%d", &N);
  S = (int*)malloc(sizeof(int)*N);
  K = (int*)malloc(sizeof(int)*N);
  for (i=0; i<N; i++) {
    scanf("%d", &(S[i]));
    scanf("%d", &(K[i]));
  }

  qsort(S, N, sizeof(int), cmp);
  qsort(K, N, sizeof(int), cmp);

  int Ws = 1;
  for (i=0; i<N-1; i++) {
    if (S[i] != S[i+1]) {
      Ws++;
    }
  }
  int Hs = 1;
  for (i=0; i<N-1; i++) {
    if (K[i] != K[i+1]) {
      Hs++;
    }
  }

  printf("%d\n", Ws*H + Hs*W - Ws*Hs - N);
  return 0;
}