#include <vector>
#include <algorithm>
#include <iostream>
#include <limits.h>

using namespace std;

struct Doll {
    int r, R;
};

// Comparator to sort dolls by outer diameter
bool compareDolls(const Doll& a, const Doll& b) {
    return a.R < b.R;
}

int minScalingOperations(vector<Doll>& dolls) {
    int n = dolls.size();
    // Sort dolls based on their outer diameters
    sort(dolls.begin(), dolls.end(), compareDolls);

    vector<int> dp(n, INT_MAX);
    dp[0] = 0;  // No scaling needed for the first doll

    for (int i = 1; i < n; ++i) {
        for (int j = 0; j < i; ++j) {
            if (dolls[j].R <= dolls[i].r) {
                dp[i] = min(dp[i], dp[j]);
            }
        }
        // Consider scaling operation if no valid nesting found
        if (dp[i] == INT_MAX) {
            dp[i] = dp[i-1] + 1;
        }
    }

    return dp[n-1];
}

int main() {
    int N;
    cin >> N;
    vector<Doll> dolls(N);
    for (int i = 0; i < N; ++i) {
        cin >> dolls[i].r >> dolls[i].R;
    }

    int result = minScalingOperations(dolls);
    cout << result << endl;
    return 0;
}