#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()) {
        int a_check = ranges[i].first; // a
        int b_check = ranges[i].second; // b
        
   
        if (i + 2 < ranges.size() && ranges[i + 2].first <= b_check) {
          
            count++;
            i += 3; 
        } else {
        
            i++;
        }
    }


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