#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <algorithm>

using namespace std;

const int N = 100100;

int noConcerts ;

struct SHOW {
    int st , en ;
};

SHOW conc[ N ] ;
int bestSol [ N ];

bool cmp ( SHOW a , SHOW b ){
    return a.en < b.en ;
}

int bnrSrch ( int val , int dr ){
    static int st , mid , sol ;

    st = 0 ;

    while ( st <= dr ){
        mid = ( st + dr ) / 2 ;

        if ( conc[ mid ].en > val ){
            dr = mid - 1 ;
        }else if ( conc[ mid ].en <= val ){
            sol = mid ;
            st = mid + 1;

        }
    }

    return sol ;
}

int main(){
    int i ;

    freopen("heavymetal.in","r",stdin);
    freopen("heavymetal.out","w",stdout);


    scanf("%d",&noConcerts );

    for ( i = 1 ; i <= noConcerts ; i++ ){
        scanf("%d%d",&conc[ i ].st ,&conc [ i ].en );
    }

    sort ( conc + 1 , conc + noConcerts + 1 , cmp );

    for ( i = 1 ; i <= noConcerts ; i ++ ){
        bestSol [ i ] = bestSol [ i - 1 ];

        int firstBehind = bnrSrch ( conc[ i ].st , i - 1 );

        bestSol [ i ] = max ( bestSol [ i ] , bestSol [ firstBehind ] + conc[ i ].en - conc [ i ].st );

    }

    printf("%d",bestSol [ noConcerts ] );

    return 0;
}