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

输入一个总的房间数，接着输入每间房已住人数以及可住总人数。若两人可住入，计算可住的房间总数。

程序分析

定义房间数n,并使用for语句，使在n次数中，输入已住人数p和可住总人数q，并比较p与q的大小，同时定义一个整数型变量i=0，若p-q>=2，则i+1，最后i的值即为可住房间数。

AC程序如下：

//CodeForces-467A
#include<iostream>
using namespace std;
int main()
{
    int n, p, q, i = 0;
    cin >> n;
    for(int j=0;j<n;j++)
    {
        cin >> p >> q;
        if (p + 2 <= q)
            i++;
    }
    cout << i;
    return 0;
}