#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 123;
const int M = 1e7 + 123;
const int inf = 1e9 + 1;
const int mod = 1e9 + 7;
const int bl = 300;
int n, a[N], b[N], cnt;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> a[i] >> b[i];
    if (abs(a[i] - b[i]) > 1) {
      cnt++;
    }
  }
  cout << cnt;
  return 0;
}
