#include<cstdio>

#include<algorithm>

#include<cstring>

#include<iostream>

#include<cmath>

#include<cctype>

#include<set>

#include<queue>

#include<vector>

#include<map>

using namespace std;

typedef long long LL;

inline int read() {

    int x=,f=;char ch=getchar();for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-;

    for(;isdigit(ch);ch=getchar())x=x*+ch-'';return x*f;

}

const int N = ;

struct Edge{

    int l, r;

    bool operator < (const Edge &A) const { return l < A.l; }

} A[N];

priority_queue<int, vector<int>, greater<int> > q;

int main() {

    int n = read();

    for (int i = ; i <= n; ++i) A[i].l = read(), A[i].r = read();

    sort(A + , A + n + );

    int ans = , cnt = ;

    q.push(A[].r);

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

        cnt ++;

        q.push(A[i].r); ;

        ans = max(ans, min(cnt, q.top() - A[i].l + ));

        while (!q.empty() && q.top() - A[i].l +  < cnt) {

            cnt --;

            q.pop();

            ans = max(ans, min(cnt, q.top() - A[i].l + ));

        }

        ans = max(ans, min(cnt, q.top() - A[i].l + ));

    }

    cout << ans;

    return ;

}