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

using namespace std;



int main() {
    map<int, std::pair<int, int>> volcanoes;
    vector<pair<int, std::pair<int, int>>> sorted;
    int samples, x, y;
    cin >> samples;

    while(samples--){
        cin >> x >> y;
        if (auto it = volcanoes.find(x) != volcanoes.end()){
            volcanoes.at(it).first = max(y, volcanoes.at(it).first);
            volcanoes.at(it).second = min(y, volcanoes.at(it).second);
        }else{
            volcanoes.insert({x, make_pair(y,y)});
        }
    }
    int distance = 0, last_x = -1, last_min = -1, last_max = -1, counter = 0;
    for (auto it:volcanoes) {
        distance += abs(it.second.first - it.second.second);
        if (last_x > 0) {
            distance += it.first - last_x;
            int from_max = abs(last_max - it.second.second) < abs(last_max - it.second.first) ?
                    abs(last_max - it.second.second) : abs(last_max - it.second.first);
            int from_min = abs(last_min - it.second.second) < abs(last_min - it.second.first) ?
                    abs(last_min - it.second.second) : abs(last_min - it.second.first);
            if (from_max < from_min) {
                distance += from_max;
            } else {
                distance += from_min;
            }
        }
        last_x = it.first;
        last_max = it.second.first;
        last_min = it.second.second;

    }

        cout << distance;




    return 0;
}