#include <stdio.h>
#include <iostream>
#define MAX 100000

using namespace std;
int interval[2][MAX], timp[MAX];
void insert_sort(int n)
{
  int i, j, aux;

  for(i = 1; i < n; i++)
  {
    j = i;
    while(j > 0 && interval[1][j] < interval[1][j - 1])
    {
      aux = interval[1][j];
      interval[1][j] = interval[1][j - 1];
      interval[1][j - 1] = aux;
      aux = interval[0][j];
      interval[0][j] = interval[0][j - 1];
      interval[0][j - 1] = aux;
      j--;
    }
  }
}
int main()
{
  FILE *fin, *fout;
  int n, i, maxi, st, dr, mij, retinem, gasit;

  fin = fopen("heavymetal.in", "r");
  fout = fopen("heavymetal.out", "w");
  fscanf(fin, "%d", &n);
  for(i = 0; i < n; i++)fscanf(fin, "%d%d", &interval[0][i], &interval[1][i]);
  insert_sort(n);
  //for(i = 0; i < n; i++)printf("%d %d\n", interval[0][i], interval[1][i]);
  for(i = 0; i < n; i++)
  {
    st = 0;
    dr = i - 1;
    gasit = 0;
    mij = retinem = 0;
    while(st <= dr && gasit == 0)
    {
      if(retinem == 0)retinem = -1;
      mij = (st + dr) / 2;
      if(interval[0][i] >= interval[1][mij])
      {
        st = mij + 1;
        retinem = mij;
      }
      else dr = mij - 1;
    }
    if(retinem != -1)timp[i] = interval[1][i] - interval[0][i] + timp[retinem];
    else timp[i] = interval[1][i] - interval[0][i];
  }
  //printf("\n");
  //for(i = 0; i < n; i++)printf("%d\n", timp[i]);
  maxi = 0;
  for(i = 0; i < n; i++)if(maxi < timp[i])maxi = timp[i];
  fprintf(fout, "%d", maxi);
  fclose( fin );
  fclose( fout );
  return 0;
}