CF467A.George and Accommodation

George has recently entered the BSUCP (Berland State University for Cool Programmers). George has a friend Alex who has also entered the university. Now they are moving into a dormitory.

George and Alex want to live in the same room. The dormitory has n rooms in total. At the moment the i-th room has p__i people living in it and the room can accommodate q__i people in total (p__i ≤ q__i). Your task is to count how many rooms has free place for both George and Alex.

乔治最近进入了BSUCP（伯兰德酷程序员国立大学）。他的朋友亚历克斯也进入了这所大学。现在他们正要搬进宿舍。

乔治和亚历克斯希望住在同一间房间。宿舍共有 $n$ 间房间。目前第 $i$ 间房间已有 $p_i$ 人入住，而该房间总共可容纳 $q_i$ 人（满足 $p_i \leq q_i$）。你的任务是计算有多少间房间还至少空余两个床位，足以同时容纳乔治和亚历克斯。

The first line contains a single integer n (1 ≤ n ≤ 100) — the number of rooms.

The i-th of the next n lines contains two integers p__i and q__i (0 ≤ p__i ≤ q__i ≤ 100) — the number of people who already live in the i-th room and the room's capacity.

第一行包含一个整数 $n$（$1 \leq n \leq 100$）—— 房间的数量。

接下来的 $n$ 行中，第 $i$ 行包含两个整数 $p_i$ 和 $q_i$（$0 \leq p_i \leq q_i \leq 100$）—— 分别表示第 $i$ 个房间中已居住的人数以及该房间的容量。

Print a single integer — the number of rooms where George and Alex can move in.

输出一个整数——乔治和亚历克斯可以入住的房间数量。