问题说明

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.

输入格式

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.

输出格式

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

3
1 1
2 2
3 3

0

来源/分类

入门 ⭐ codeforces 800分