#include <iostream>
#include <vector>
#include <algorithm>

int main()
{
    long long W, H;
    long long sc, kc;
    long long N;
    long long r;
    std::vector<int> S, K;
    std::vector<bool> has_s, has_k;
    std::cin >> W >> H >> N;
    S.resize(N);
    K.resize(N);
    for (long long i = 0; i < N; i++) {
        std::cin >> S[i] >> K[i];
    }
    has_s.resize(W, false);
    has_k.resize(H, false);
    for (long long i = 0; i < N; i++) {
       has_s[S[i] - 1] = true;
       has_k[K[i] - 1] = true;
    }
    sc = std::count(has_s.begin(), has_s.end(), true);
    kc = std::count(has_k.begin(), has_k.end(), true);
    r = sc * H + kc * W - sc * kc - N;
    std::cout << r << std::endl;
}