#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const long long INFLL = 0x3f3f3f3f3f3f3f3fLL;
const double eps = 1e-8;
const int MOD = 1e9 + 7;
const int MAXN = 3e3 + 50;
const int MAXM = 2e4 + 50;
int r, c, n, m[MAXN][MAXN * 2], id[MAXN][MAXN * 2];
int p[MAXN * MAXN * 2], rk[MAXN * MAXN * 2];
int d[8][2] = {{0, -1}, {1, -1}, {1, 0},  {1, 1},
               {0, 1},  {-1, 1}, {-1, 0}, {-1, -1}};
stack<pair<int*, int>> s;
void Record(int& var, int x) {
  s.push(make_pair(&var, var));
  var = x;
}
void Rollback(int upd) {
  while (!s.empty()) {
    if (upd) *s.top().first = s.top().second;
    s.pop();
  }
}
int Find(int x) {
  while (x != p[x]) x = p[x];
  return x;
}
void Union(int a, int b) {
  int x = Find(a), y = Find(b);
  if (x == y) return;
  if (rk[x] <= rk[y]) {
    Record(p[x], y);
    if (rk[x] == rk[y]) {
      Record(rk[y], rk[y] + 1);
    }
  } else {
    Record(p[y], x);
  }
}
void Add(int x, int y) {
  for (int i = 0; i < 8; i++) {
    int xx = x + d[i][0];
    int yy = y + d[i][1];
    if (yy < 1) yy += 2 * c;
    if (yy > 2 * c) yy -= 2 * c;
    if (xx < 1 || xx > r) continue;
    if (m[xx][yy]) Union(id[x][y], id[xx][yy]);
  }
}
int main() {
  while (~scanf("%d%d%d", &r, &c, &n)) {
    memset(m, 0, sizeof(m));
    int t = 0;
    for (int i = 1; i <= r; i++)
      for (int j = 1; j <= 2 * c; j++) id[i][j] = t++;
    for (int i = 0; i < t; i++) {
      p[i] = i;
      rk[i] = 0;
    }
    int ans = 0;
    while (!s.empty()) s.pop();
    while (n--) {
      int x, y;
      scanf("%d%d", &x, &y);
      m[x][y] = m[x][y + c] = 1;
      Add(x, y);
      Add(x, y + c);
      if (Find(id[x][y]) == Find(id[x][y + c])) {
        m[x][y] = m[x][y + c] = 0;
        Rollback(1);
      } else {
        ans++;
        Rollback(0);
      }
    }
    printf("%d\n", ans);
  }
  return 0;
}
