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 pi people living in it and the room can accommodate qi people in total (pi ≤ qi). Your task is to count how many rooms has free place for both George and Alex.
Input
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 pi and qi (0 ≤ pi ≤ qi ≤ 100) — the number of people who already live in the i-th room and the room's capacity.
Output
Print a single integer — the number of rooms where George and Alex can move in.
Examples
Input
3
1 1
2 2
3 3
Output
0
Input
3
1 10
0 10
10 10
Output
2
问题简述
George和Alex想住在酒店的同一间房间。该酒店有一共有n（1<=n<=100）间房间,第i间房可以容纳qi个人，现在住了pi个人。现在要计算出有多少间房间可以让两个人一起住。
输入要求：第一行是房间的总数n;
第二行是第i间房可以容纳的总数qi和已经入住的人数pi；
每次输入三组数据，然后计算。
问题分析和程序说明
依次输入多个房间，所以要在一开始用while语句来实现该循环。要输出一共有多少个房间满足条件则另外设定判断语句i<n,并再次设定一个条件qi-pi>=2,定义一个整型a来累加次数。