#include <bits/stdc++.h>
using namespace std;
int counter(vector<int> vec,int n){
    int i = 0;
    int c = 0;
    int l = vec.size();
    for(i=0;i<l;i++){
        if(vec[i] == n) c++;
    }
    return c;
}
int main(){
    int W,H,N;
    int sum = 0;
    cin >> W >> H >> N;
    vector<int> S(N+1,0);
    vector<int> K(N+1,0);
    for(int i=1;i<=N;i++){
        cin >> S[i];
        cin >> K[i];
    }
    for(int i=1;i<=W;i++){
        int c1 = counter(S,i);
        if(c1 != 0) sum += H-c1;
    }
    int c3 = 0;
    for(int i=1;i<=W;i++){
        if(counter(S,i) != 0) c3++;
    }
    for(int i=1;i<=H;i++){
        int c2 = counter(K,i);
        if(c2 != 0) sum += W - c3;
    }
    cout << sum << endl;
    return 0;
}