#include <iostream>
#include <iomanip>

#include <algorithm>
#include <math.h>

#include <string>
#include <list>
/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////

int main(void){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed;//
    //cout << setprecision(6);//
	
	int W;
	cin>>W;//[1,10^6]
	int H;
	cin>>H;//[1,10^6]
	int N;
	cin>>N;

	int S[100];
	int K[100];

	for( int i = 0 ; i < N ; ++i ){
		cin>>S[i]>>K[i];
	}
	sort(S,S+N);
	sort(K,K+N);
	int ss = 0;
	int kk = 0;
	int temp = -1;
	for(int i=0;i<N;++i){
		if(temp != S[i]){
			temp = S[i];
			++ss;
		}
	}
	temp = -1;
	for(int i=0;i<N;++i){
		if(temp != K[i]){
			temp = K[i];
			++kk;
		}
	}
	////////////ひえー逆だった
	int ans = kk * W + ss * H - ss * kk - N;
	//100*10^6 * 2 -10^4 - 10^2
	//10^8 * 2
	P(ans);
	return 0;
}