#include <iostream>

#include <stdio.h>

#include <algorithm>

using namespace std;

#define LL long long

struct line

{

    int b, e;

}L[];

int n;

int cmp(line a, line b)

{

    if (a.b != b.b)

        return a.b < b.b;

    else

        return a.e < b.e;

}

int main()

{

    //freopen("1.txt", "r", stdin);

    scanf("%d", &n);

    for (int i = ; i < n; i++)

        scanf("%d%d", &L[i].b, &L[i].e);

    sort(L, L+n, cmp);

    int maxlen = , end = L[].e;

    for (int i = ; i < n; i++) {

        maxlen = max(maxlen, min(end, L[i].e)-L[i].b);

        end = max(end, L[i].e);

    }

    printf("%d\n", maxlen);

    return ;

}