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

using namespace std;

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

    vector<int> directions(n);
    vector<int> arrival_times(n);

    for (int i = 0; i < n; i++) {
        cin >> directions[i];
        cin >> arrival_times[i];
    }

    sort(arrival_times.begin(), arrival_times.end());

    int total_waiting_time = 0;
    for (int i = 0; i < n; i++) {
        int pedestrian_waiting_time = arrival_times[i] - i;
        total_waiting_time += pedestrian_waiting_time;
    }

    cout << total_waiting_time << endl;

    return 0;
}