#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<vector>
#include<list>
#include<algorithm>
#include<utility>
#include<complex>
#include<functional>
using namespace std;
bool mark[1000001],num[1000001];
#define LL long long
int main(void){
	LL H, W, h = 0, w = 0;int  N;
	cin >> H >> W >> N;
	for (int i = 0; i < N; i++)
	{
		int a, b;
		cin >> a >> b;
		if (mark[a] == false)h++;
		if (mark[b] == false)w++;
		mark[a] = mark[b] = true;
	}
	cout << h*W + w*H - h*w - N << endl;;
	return 0;
}