#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
	int n;
	cin >> n;

	vector<int> begin(24, 0);
	vector<int> end(24, 0);

	for (int i = 0; i < n; i++)
	{
		int temp1 = 0, temp2 = 0;
		cin >> temp1 >> temp2;
		begin[temp1-1]++;
		end[temp2-1]++;
	}

	int days = n, temp2 = 0;

	for (int i = 0; i < 23; i++)
	{
		if (begin[i]<=end[i])
		{
			days -= begin[i];
		}
		else
		{
			days -= end[i];
		}
	}

	cout << days;
}