#include<iostream>
using namespace std;
int main(){
    int W,H,N,S,K,ans;
    bool mark[1000001] = {};
    bool num[1000001] = {};
    int Wc = 0;
    int Hc = 0;
    cin >> W >> H >> N;
    for(int i=0;i<N;i++){
        cin >> S >> K;
        if(! mark[S]){
            mark[S] = true;
            Wc++;
        }
        if(! num[K]){
            num[K] = true;
            Hc++;
        }
    }
    ans = Wc*H + Hc*W - Wc*Hc -N;
    cout <<  ans << endl;
    return 0;
}