#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <time.h>
 
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef LL ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<ut,pr> ppr;
typedef priority_queue<pr,Vpr, greater<pr> > PQ;
const int SIZE=1e+6 + 1;
const ut INF=1<<30;
const ld eps=1e-6;
const LL mod=1e+9 + 7;

vector<LL> M, N;

int main() {
	cin.tie(0);
    ios::sync_with_stdio(false);
    LL W, H, S;
    LL m[128], n[128];
    cin >> W >> H >> S;
    REP(i,S){
    	cin >> m[i] >> n[i];
    	M.PB(m[i]);
    	N.PB(n[i]);
    }
    sort(BE(M));
    sort(BE(N));
    M.erase(unique(BE(M)), M.end());
    N.erase(unique(BE(N)), N.end());
	LL ans = 0;
	ans += H * M.size();
	ans += W * N.size();
	ans -= M.size() * N.size() + S;
    cout << ans << endl;
 	return 0;
}