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

int main(int argc, char* argv[])
{
    int X, Y, N;
    while (cin >> X >> Y >> N) {
        if (!X && !Y && !N) break;
        vector<bool> cols;
        vector<bool> rows;
        vector<bool> diag1;
        vector<bool> diag2;
        cols.resize(X, true);
        rows.resize(Y, true);
        diag1.resize(X+Y-1, true);
        diag2.resize(X+Y-1, true);
        int d2offset = Y-1;
        for (int i=0; i<N; i++) {
            int x, y;
            cin >> x >> y;
            x--;
            y--;
            cols[x] = false;
            rows[y] = false;
            diag1[x+y] = false;
            diag2[x-y+d2offset] = false;
        }
        int places = 0;
        for (int y=0; y<Y; y++) {
            if (!rows[y]) continue;
            for (int x=0; x<X; x++) {
                if (cols[x] && diag1[x+y] && diag2[x-y+d2offset]) places++;
            }
        }
        cout << places << endl;     
    }
    return 0;
}