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
判断房子能住的人减去已经住下的人是否大于等于2;
当>=2时,George及其朋友就能住;
代码如下

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