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 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
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：
1 #include<bits/stdc++.h> 2 using namespace std; 3 int main(){ 4 int n,p,q,num=0; 5 cin>>n; 6 while(n--){ 7 cin>>p>>q; 8 if(q-p>=2)num++; 9 } 10 cout<<num<<endl; 11 return 0; 12 }