2 5 10
2 2
1 1
1 4
2 1
1 2
1 5
2 4
2 5
1 3
2 3
 2 2 2
1 1
2 2
 3 3 9
1 1
1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3
 7 5 35
5 3
3 5
1 1
2 5
6 4
7 2
5 1
3 4
6 5
7 3
4 1
2 2
4 2
2 4
4 3
3 3
6 1
1 2
4 5
1 3
2 1
5 5
7 5
7 1
6 2
1 4
1 5
3 2
4 4
5 2
2 3
6 3
7 4
5 4
3 1
 1 5 4
1 1
1 2
1 4
1 5
 1 1 1
1 1
 5 7 21
4 4
4 5
5 5
5 6
5 7
5 1
5 2
4 2
3 2
3 1
3 7
3 6
2 6
1 6
1 7
1 1
1 2
1 3
1 4
2 4
3 4
 2 1 1
1 1
 2 2 4
2 1
1 1
1 2
2 2
 3000 3000 1
2222 738
 5 7 35
1 2
2 3
5 1
5 7
4 4
5 3
3 1
2 6
4 5
2 7
4 1
2 1
2 2
1 7
5 6
3 6
4 6
1 6
1 1
3 3
3 4
4 2
2 5
5 5
3 5
2 4
1 5
1 3
4 3
5 4
1 4
3 7
4 7
3 2
5 2
 5 4 1
4 1
 3 4 12
2 3
3 2
2 2
2 1
1 2
3 1
1 4
1 3
3 3
2 4
3 4
1 1
 3 3 3
1 1
2 2
3 3

8
 1
 6
 26
 4
 0
 20
 0
 2
 1
 28
 1
 9
 3

#include <bits/stdc++.h>
using namespace std;
int r, c, n;
bool f[3001][6001];
int rt[3000 * 6000 + 1];
int root(int u) {
  while (rt[u] > 0) u = rt[u];
  return u;
}
vector<pair<int, int>> rb;
void unite(int u, int v) {
  u = root(u);
  v = root(v);
  if (u == v) return;
  if (rt[u] > rt[v]) swap(v, u);
  rb.push_back({u, rt[u]});
  rb.push_back({v, rt[v]});
  rt[u] += rt[v];
  rt[v] = u;
}
void rollBack() {
  while (!rb.empty()) {
    rt[rb.back().first] = rb.back().second;
    rb.pop_back();
  }
}
int id(int x, int y) { return (x - 1) * c * 2 + y; }
const int cx[] = {-1, -1, -1, 0, 0, 1, 1, 1};
const int cy[] = {-1, 0, 1, -1, 1, -1, 0, 1};
void turnOn(int x, int y) {
  f[x][y] = 1;
  int i = id(x, y);
  for (int k = 0; k < 8; k++) {
    int xx = x + cx[k];
    int yy = y + cy[k];
    if (xx < 1 || xx > r) continue;
    if (yy < 1 || yy > c * 2) continue;
    if (f[xx][yy]) unite(id(xx, yy), i);
  }
}
void turnOff(int x, int y) { f[x][y] = 0; }
bool sameComponent(int x, int y, int u, int v) {
  return root(id(x, y)) == root(id(u, v));
}
int main() {
  cin >> r >> c >> n;
  for (int i = r * c * 2; i >= 1; i--) rt[i] = -1;
  int ans = 0;
  for (int i = 1, x, y; i <= n; i++) {
    cin >> x >> y;
    turnOn(x, y);
    turnOn(x, y + c);
    if (sameComponent(x, y, x, y + c)) {
      turnOff(x, y);
      turnOff(x, y + c);
      rollBack();
    } else {
      ans++;
      rb.clear();
    }
  }
  cout << ans;
}
