#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  int cc = 0;
  for (int i = 0; i < n; ++i) {
    int a, b;
    scanf("%d%d", &a, &b);
    if (b >= a + 2) ++cc;
  }
  printf("%d\n", cc);
}
