A - George and Accommodation

Problem description

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.

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 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.

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
解题思路：统计房间内剩余人数不小于2的房间总数（两个人住在同一间），水过！
AC代码：

#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,p,q,num=0;
    cin>>n;
    while(n--){
        cin>>p>>q;
        if(q-p>=2)num++;
    }
    cout<<num<<endl;
    return 0;
}