ifstream cin("lifeguards.in");
  ofstream cout("lifeguards.out");
  int t; cin >> t;
  pair <int, int> time[t];
  
  int max = 0;
  
  for (int i = 0; i < t; ++i)
  {
    cin >> time[i].first >> time[i].second;
  }

  for (int i = 0; i < t; ++i)
  {
    int arr[1001] = {0};

    for (int j = 0; j < t; ++j)
    {
      if (i != j){
        for (int k = time[j].first; k <= time[j].second; ++k)
        {
          arr[k]++;
        }      
      }
    }
    int ans = 0;
    for (int o = 0; o < 1001; ++o)
      {
        if (arr[o] > 0) {
          ans ++;
          if (ans > max) max = ans;
        }
        else ans = 0;
    }
  }
  
  
  cout << max;