#include<iostream>
#include<vector>

int main() {
    int W, H, N, S, K;
    std::cin >> W;
    std::cin >> H;
    std::cin >> N;
    std::vector<bool> marks(W, false), numbers(H, false);
    for (int i = 0; i < N; i++) {
        std::cin >> S >> K;
        S--;
        K--;
        marks.at(S) = true;
        numbers.at(K) = true;
    }
    int m_ct = 0, n_ct = 0;
    for (const auto &mark: marks) {
        if (mark) { m_ct++; }
    }
    for (const auto &num: numbers) {
        if (num) { n_ct++; }
    }
    int ans = m_ct * H + n_ct * W - m_ct * n_ct - N;
    std::cout << ans << std::endl;
}