#include <bits/stdc++.h>
using namespace std;
int main() {
    #ifdef DEBUG
    std::ifstream in("/home/share/inputf.in");
    std::cin.rdbuf(in.rdbuf());
    #endif
    int64_t W, H, N;
    cin >> W >> H >> N;
    set<int64_t> w, h;
    for(int i = 0; i < N; i++) {
        int64_t S, K;
        cin >> S >> K;
        w.insert(S), h.insert(K);
    }
    int64_t ans = W * H - (W - w.size()) * (H - h.size()) - N;
    cout << ans << endl;
    return 0;
}