#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

int main() {
    ifstream fin("heavymetal.in");
    ofstream fout("heavymetal.out");
    
    int N, i, j, ma;
    fin >> N;
    pair<int, int> ore[N];
    int m[N];
    for(i=0; i<N; ++i) {
        fin >> ore[i].first >> ore[i].second;
    }
    sort(ore, ore+N, [](const std::pair<int, int> &left, const std::pair<int, int> &right) {
        return left.second < right.second;
    });

    m[0] = ore[0].second - ore[0].first;

    fout << m[N-1];

    return 0;
}