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

void main(){
	auto W = readln().strip().to!long;
	auto H = readln().strip().to!long;
	auto N = readln().strip().to!int;

	int[] S = new int[](N);
	int[] K = new int[](N);

	foreach(int i; 0 .. N) {
		auto buf = readln().strip().split().map!(to!int)();
		S[i] = buf[0];
		K[i] = buf[1];
	}

	S.sort();
	K.sort();

	immutable int sw = S.uniq().array().length.to!int;
	immutable int kw = K.uniq().array().length.to!int;

	writeln( H*W - (H-sw)*(W-kw) - N);
}