#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int W,H; cin >> W >> H;
    vector<bool> S(W),K(H);
    int N; cin >> N;
    int m = 0,n = 0,answer = -N;
    while(N--){
        int s,k; cin >> s >> k;
        s--; k--;
        if(!S.at(s)) S.at(s) = true,m++;
        if(!K.at(k)) K.at(k) = true,n++; 
    }
    cout << answer+m*H+W*n-m*n << endl;
}