#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <utility>
#include <stack>
#include <stack>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <list>

#define FILL(a,b) fill(a,a+(sizeof(a)/sizeof(a[0])),b)
#define FOR(a,b,c) for(int a=b; a<=c; a++)
#define DOWNFOR(a,b,c) for(int a=b; a>=c; a--)
#define SIZEOF(a) (sizeof(a)/sizeof(a[0]))
#define FORARR(i,a) for(unsigned i=0; i<SIZEOF(a); i++)
#define FOREACH(a,b) for(__typeof((b).begin()) a=(b).begin(); a!=(b).end(); a++)
#define GETI(a) scanf("%d", &a)

using namespace std;

int main(void)
{
  int X, Y, N;
  while (scanf("%d %d %d", &X, &Y, &N) == 3 && !(X == 0 && Y == 0 && N == 0)) {
    bool rows[20001] = {0};
    bool cols[20001] = {0};
    bool diagplus[40001] = {0};
    bool diagminus[40001] = {0};
    FOR(i,1,N) {
      int x, y;
      scanf("%d %d", &x, &y);
      rows[y] = true;
      cols[x] = true;
      diagplus[x+y] = true;
      diagminus[x-y+20000] = true;
    }
    int num = 0;
    FOR(x,1,X) {
      if (cols[x]) continue;
      FOR(y,1,Y) {
	if (rows[y]) continue;
	if (diagplus[x+y]) continue;
	if (diagminus[x-y+20000]) continue;
#ifdef DEBUG
printf("%d %d is free\n", x, y);
#endif
	num++;
      }
    }
    printf("%d\n", num);
  }
  
  
  
    return 0;
}