#include<stdio.h>
#include<algorithm>
using namespace std;
struct st
{
    int st,dr;
};
st s[100005];
int sol[100005];
bool cmp(st a,st b)
{
    return a.dr<b.dr;
}
int bs(int st,int dr,int poz)
{
    int med,last=0;

    while(st<=dr)
    {
        med=(dr+st)/2;
        if(s[med].dr<=s[poz].st)
        {
            st=med+1;
            last=med;
        }
        else
        {
            dr=med-1;
        }
    }
    return last;
}
int main()
{
    freopen("heavymetal.in","r",stdin);
    freopen("heavymetal.out","w",stdout);
    int n,i,rez;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
        scanf("%d%d",&s[i].st,&s[i].dr);

    sort(s+1,s+n+1,cmp);
    for(i=1;i<=n;i++)
    {
        rez=bs(1,i,i);
        sol[i]=sol[i-1];
        if(sol[rez]+(s[i].dr-s[i].st)>sol[i])
            sol[i]=sol[rez]+(s[i].dr-s[i].st);
    }
    printf("%d\n",sol[n]);
    return 0;
}