#include <bits/stdc++.h>
using namespace std;
#define LL long long
int main(void){
	LL H, W, h = 0, w = 0;int  N;
	cin >> H >> W >> N;
    vector<bool> mark(H,false),num(W,false);
	for (int i = 0; i < N; i++)
	{
		int a, b;
		cin >> a >> b;
		if (mark[a] == false)h++;
		if (num[b] == false)w++;
		mark[a] = num[b] = true;

	}
	cout << h*W + w*H - h*w - N << endl;;
	return 0;
}