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

typedef long long ll;

const int kMAX_N = 110;

int W, H, N;
int S[kMAX_N], K[kMAX_N];

void Solve() {
    set<int> mark, number;
    ll answer;

    for (int i = 0; i < N; i++) {
        mark.insert(S[i]);
        number.insert(K[i]);
    }

    answer = (ll)mark.size() * (ll)H +
                (ll)number.size() * (ll)W -
                    (ll)N - (ll)mark.size() * (ll)number.size();

    cout << answer << endl;
}

int main() {
    cin >> W >> H >> N;

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

    Solve();

    return 0;
}