#include <bits/stdc++.h>
using namespace std;

int iW[ 1000010 ];
int iH[ 1000010 ];

int main()
{
int i;
int W;
int H;
int N;
int S;
int K;
int iSum;
int iCntW;
int iCntH;

	cin >> W;
	cin >> H;
	cin >> N;

	for( i = 0; i < N; i++ )
	{
		cin >> S;
		cin >> K;
		iW[ S ]++;
		iH[ K ]++;
	}

	iCntW = 0;
	for( i = 1; i <= W; i++ )
	{
		if( iW[ i ] > 0 ) iCntW++;
	}

	iCntH = 0;
	for( i = 1; i <= H; i++ )
	{
		if( iH[ i ] > 0 ) iCntH++;
	}
	

	cout << iCntH * W + iCntW * H - iCntH * iCntW - N << endl;

	return 0;
}