#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int main() {
    long long h, w, n;
    cin >> h >> w >> n;
    set<long long> st, st1;
    for (int i = 0; i < n; i++) {
        long long s, k;
        cin >> s >> k;
        st.insert(s);
        st1.insert(k);
    }
    long long l = st.size() * w - n;
    long long r = (h - st.size()) * st1.size();
    cout << l + r << endl;
}