#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long ll;
typedef long double ld;
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <cmath>
#include <iomanip>
#include <limits>
#include <unordered_map>
#include <set>
#include <numeric>
#include <iomanip>
 
int main() {
    // Number of people
    int n; 
    cin >> n;
    vector<pair<int, int>> ranges; // to store (a, b) pairs

    // Read input ranges
    for (int i = 1; i <= n; i++) {
        int a, b; 
        cin >> a >> b;
        if (b - a < 2) continue; // skip ranges that can't form a team
        ranges.push_back(make_pair(a, b));
    }

    // sort ranges by their starting point
    sort(ranges.begin(), ranges.end());

    int count = 0; 
    int i = 0;


        while (i < ranges.size()) {
       
        if (i + 2 < ranges.size()) {
            int a1 = ranges[i].first;  
            int b1 = ranges[i].second;  
            int a2 = ranges[i + 1].first;
            int b2 = ranges[i + 1].second; 
            int a3 = ranges[i + 2].first; 
            int b3 = ranges[i + 2].second;
            
       
            if (a1 <= a2 && b1 >= a3 &&  
                a2 <= a1 && b2 >= a3 &&  
                a3 <= a1 && b3 >= a2) {  
                
                count++;
                i += 3; 
            } else {
                i++; 
            }
        } else {
            break; 
        }
    }

    cout << count << "\n"; 
    return 0;
}