#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{

    int X,Y,N;
    int r,s;
    while (1) {
        int ans=0;
        vector <int> riadky,stlpce,d1,d2;
        cin >> X >> Y >> N;
        if (N==0) {cout << X*Y<< endl; continue;}
        if (X==0 && Y==0 && N==0) break;
        for (int i=1; i<=N; i++) {
            cin >> r >> s;
            riadky.push_back(r);
            stlpce.push_back(s);
            d1.push_back(r+s-1);
            d2.push_back(r+Y-s+1);
        }

        sort(riadky.begin(),riadky.end());
        sort(stlpce.begin(),stlpce.end());
        sort(d1.begin(),d1.end());
        sort(d2.begin(),d2.end());
        for (int i=1; i<=X;i++) {
            if (binary_search(riadky.begin(),riadky.end(),i)) {continue;}
            for (int j=1; j<=Y; j++) {
                if (binary_search(stlpce.begin(),stlpce.end(),j)) {continue;}
                if (binary_search(d1.begin(),d1.end(),i+j-1)) {continue;}
                if (binary_search(d2.begin(),d2.end(),i+Y-j+1)) {continue;}
                ans++;

            }
        }
        cout << ans << endl;
    }
    return 0;
}