#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int res = 0;
  for (int i = 0; i < n; i++) {
    int a, b;
    cin >> a >> b;
    if (b - a >= 2) res++;
  }
  cout << res;
  return 0;
}
