#include <iostream>
#include <unordered_map>
using namespace std;

int main(void) {
    int W, H, N, S, K;
    unordered_map<int, int> numbers, mark;
    cin >> W >> H >> N;

    for (int i = 0; i < N; i++) {
        cin >> S >> K;
        mark[S] = 1;
        numbers[K] = 1;
    }

    int msize = mark.size();
    int nsize = numbers.size();

    //cout << "mark size: " << msize << ", number size: " << nsize << endl;

    int result = H * msize + W * nsize - msize * nsize - N;
    cout << result << endl;

    return 0;
}