为什么都TLE啊啊啊啊啊！！！！

var
  x,y,j,k,n,m,s,i:longint;
  h,l:array[0..20001] of boolean;
  a,b:array[-40001..40001] of boolean;
begin
  readln(n,m,k);
  fillchar(h,sizeof(h),true);
  fillchar(l,sizeof(l),true);
  fillchar(a,sizeof(a),true);
  fillchar(b,sizeof(b),true);
  if k=0 then begin
    write(n*m);halt;
  end;
  for i:=1 to k do begin
    readln(x,y);
    h[x]:=false;l[y]:=false;
    a[x+y]:=false;b[x-y]:=false;
  end;
  for i:=1 to n do begin
    for j:=1 to m do begin
      if not(h[i]) then break;
      if (l[j])and(a[i+j])and(b[i-j]) then inc(s);
      if s=0 then break;
    end;
    if s=0 then break;
  end;
  write(s);
end.