#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
#include <map>
#include <iomanip>
using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector< pair<long long, long long> > v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i].first >> v[i].second;
    v[i].second--;
  }
  sort(v.begin(), v.end(), [](const pair<long long, long long>& a, const pair<long long, long long>& b) {
    if (a.second == b.second) {
      return a.first < b.first;
    }
    return a.second < b.second;
  });
  vector<long long> dp(n);
  vector<long long> a(n);
  for (int i = 0; i < n; i++) {
    a[i] = v[i].second;
  }
  for (int i = 0; i < n; i++) {
    auto it = lower_bound(a.begin(), a.end(), v[i].first);
    dp[i] = v[i].second - v[i].first + 1;
    if (it != a.begin()) {
      dp[i] += dp[prev(it) - a.begin()];
    }
    if (i > 0) {
      dp[i] = max(dp[i], dp[i - 1]);
    }
  }
  cout << dp[n - 1] << '\n';
  return 0;
}