#include <iostream>
#include <vector>
#include <fstream>
#include <algorithm>
#include <string>
#include <cmath>

using namespace std;

int main()
{
	ifstream fin;
	ofstream fout;

	fin.open("DATA4.txt");
	fout.open("OUT4.txt");

	for (unsigned int i = 0; i < 5; i++)
	{
		int number = 0;
		int num;
		fin >> num;
		for (int j = 0; j < num; j++)
		{
			int temp1, temp2;
			fin >> temp1 >> temp2;
			if (temp1 > temp2)
			{
				if (temp2 == temp1 - 1)
					number += 1;
			}
			else if (temp2 > temp1)
			{
				if (temp1 == temp2 - 1)
					number += 1;
			}
		}
		number = number - 1;
		fout << number << endl;
	}
	fout.close();
	fin.close();
}