module main;

import std;

void main()
{
	// 入力
	auto W = readln.chomp.to!long;
	auto H = readln.chomp.to!long;
	auto N = readln.chomp.to!int;
	auto S = new long[](N), K = new long[](N);
	auto sSet = new RedBlackTree!long(), kSet = new RedBlackTree!long();
	foreach (ref s, ref k; lockstep(S, K)) {
		readln.chomp.formattedRead("%d %d", s, k);
		sSet.insert(s);
		kSet.insert(k);
	}
	// 答えの計算
	long ans = sSet.length * H + kSet.length * W - sSet.length * kSet.length - N;
	// 答えの出力
	writeln(ans);
}