#include <bits/stdc++.h>
#define FOR(i,bg,ed) for(ll i=(bg);i<(ed);i++)
#define REP(i,n) FOR(i,0,n)
#define MOD 1000000007
//#define int long long
using namespace std;
typedef long long ll;
typedef vector<vector<ll>> mat;
const int INF = 1e9;



signed main()
{
    int W, H, N;
    int S, K;

    cin >> W >> H >> N;
    set<int> mark, num;
    REP(i,N) {
        cin >> S >> K;
        mark.insert(S);
        num.insert(K);
    }

    cout << H * mark.size() + W * num.size() - mark.size() * num.size() - N << endl;
}