#include <bits/stdc++.h>

using namespace std;

using ll = long long;

int main() {
  ll P, Q;
  cin >> P >> Q;

  int N;
  cin >> N;

  ll g = gcd(P - Q, gcd(Q - P, P + Q));

  int ans = 0;
  while (N--) {
    ll X, Y;
    cin >> X >> Y;

    if ((X + Y) % g == 0) ++ans;
  }

  cout << ans << endl;
  return 0;
}