Submission

Score: 0

User: vachirasawin

Problemset: ห้องสมุดเมือง 3M

Language: cpp

Time: 0.002 second

Submitted On: 2026-03-12 22:10:19

// grader-chan
// c2_ds66_3m.cpp | c2_ds66_3m

#include <bits/stdc++.h>
using namespace std;

int n;
vector<pair<int, int>> books;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    cin >> n;

    while (n--) {
        int xi, yi;
        cin >> xi >> yi;
        books.push_back({xi, yi});
    }

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

    long long total = 0;
    int curr = books[0].first;
    for (auto const& book : books) {
        int xi = book.first;
        int yi = book.second;

        if (xi >= curr) {
            total += (yi - xi);
            curr = yi;
        } else if (yi >= curr) {
            total = (yi - curr);
            curr = yi;
        }
    }

    cout << total / 2 - 1 << endl;

    return 0;
}