#include<fstream>
#include<algorithm>
#define DIM 10001
using namespace std;
ifstream fin("heavymetal.in");
ofstream fout("heavymetal.out");
struct band
{       int start, end,in;};
int compare(band a, band b)
{
    return a.start<b.start || (a.start==b.start && a.end<b.end);
}
int main()
{
    band a[DIM];
    int i,j,n,total,s,x;
    fin>>n;
    for(i=1;i<=n;++i)
    {
        fin>>a[i].start;
        fin>>a[i].end;
    }
    sort(a+1,a+n+1,compare);
    total=0;
    x=0;
    s=0;
    int max=0,k=0;
    for(j=1;j<=n;++j)
    {
      x=0;
      s=0;k++;
      for(i=k;i<=n;++i)
        if(a[i].start>=x)
        {
            total=a[i].end-a[i].start;
            x=a[i].end;
            s=s+total;
        }
        if(s>max) max=s;
    }
    fout<<max+1;
    return 0;
}