//Problem pavare from Infoarena
#include <cmath>

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

ifstream fin("pavare.in");
ofstream fout("pavare.out");

const int INF = 1 << 30;
const int MAX_N = 151;
const int MAX_M = 16;

int N, M, K;
bool good[MAX_N][MAX_M];
int d[MAX_N][MAX_M][1 << MAX_M];

int main() {
  fin >> N >> M >> K;

  for (int i = 0, x, y; i < K; i += 1) {
    fin >> x >> y;
    good[x - 1][y - 1] = 1;
  }

  for (int i = 1; i < N; i += 1) {
    for (int mask = 0; mask < (1 << M); mask += 1) {
      if (mask & 1) {
        d[i][0][mask] = d[i - 1][M - 1][mask ^ 1];
      } else {
        d[i][0][mask] = d[i - 1][M - 1][mask];
      }
    }
    for (int j = 1; j < M; j += 1) {
      bool bad = (not (good[i][j] || good[i - 1][j] || good[i][j - 1] || good[i - 1][j - 1]));
      cerr << bad << endl;
      for (int mask = 0; mask < (1 << M); mask += 1) {
        if ((1 << j) & mask) {
          cerr << "0  ";
          d[i][j][mask] = d[i][j - 1][mask ^ (1 << j)];
        } else {
          d[i][j][mask] = d[i][j - 1][mask];

          if (bad && !((1 << (j - 1)) & mask)) {
            cerr << "2  ";
            d[i][j][mask] = max(d[i][j][mask],
              d[i][j - 2][mask ^ (1 << j) ^ (1 << (j - 1))] + 1);
          } else {
            cerr << "1  ";
          }
        }

        cerr << i << ' ' << j << ' ' << mask << ' ' << d[i][j][mask] << endl;
        // cerr << ((1 << j) & mask) << ' ' << ((1 << (j - 1)) & mask) << endl;
      }
    }
    cerr << endl;
  }
  fout << d[N - 1][M - 1][0];
  return 0;
}