import std.algorithm, std.array, std.container, std.range;
import std.string, std.conv, std.math;
import std.stdio, std.typecons;

alias Tuple!(int, "s", int, "k") card;

void main()
{
  auto w = readln.chomp.to!int;
  auto h = readln.chomp.to!int;
  auto n = readln.chomp.to!int;
  auto ci = iota(n).map!((i) {
    auto rd = readln.split.map!(to!int);
    return card(rd[0], rd[1]);
  }).array;

  auto s = ci.map!(c => c.s).uniq.array.length;
  auto k = ci.map!(c => c.k).uniq.array.length;

  writeln(w * k + s * h - s * k - ci.length);
}