#include <iostream>
#include <vector>
using namespace std;
vector <int> X;
vector <int> Y;
vector <short> S;
int main ()
{
    long long n,m;
    int k;
    cin >> n >> m >> k;
    if(k == n*m)
    {
        cout << 0 << '\n';
        return 0;
    }
    short umn = 0;
    int ostm = m % 2;
    int ostn = n % 2;
    for(int i = 0 ; i < k ; ++i)
    {
        int x,y;
        cin >> x >> y;
        int res1 = n / 2 + n % 2 ,res2 = m / 2 + m % 2;
        if(m > n && x == res1 && ostm == 1)
            ++umn;
        if(m < n && y == res2 && ostn == 1)
            ++umn;
        if(x > res1)
        {
            x -= (n+1);
            x = -x;
        }
        if(y > res2)
        {
            y -= (m+1);
            y = -y;
        }
        int s = X.size();
        int ind = -1;
        for(int i = 0 ; i < s ; ++i)
        {
            if(X[i] == x && Y[i] == y){
                ind = i;
                break;
            }
        }
        if(ind == -1){
            X.push_back(x);
            Y.push_back(y);
            S.push_back(1);
        }else{
            ++S[ind];
        }

    }
    int s = X.size();
    int sum = k;
    for(int i = 0 ; i < s ; ++i)
    {
        sum += 4-S[i];
    }
    cout << sum - umn*2 << '\n';
    return 0;
}