題目連結：https://codeforces.com/contest/1029/problem/C

C. Maximal Intersection

time limit per test

3 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

You are given nn segments on a number line; each endpoint of every segment has integer coordinates. Some segments can degenerate to points. Segments can intersect with each other, be nested in each other or even coincide.

The intersection of a sequence of segments is such a maximal set of points (not necesserily having integer coordinates) that each point lies within every segment from the sequence. If the resulting set isn't empty, then it always forms some continuous segment. The length of the intersection is the length of the resulting segment or 00 in case the intersection is an empty set.

For example, the intersection of segments [1;5][1;5] and [3;10][3;10] is [3;5][3;5] (length 22), the intersection of segments [1;5][1;5] and [5;7][5;7] is [5;5][5;5](length 00) and the intersection of segments [1;5][1;5] and [6;6][6;6] is an empty set (length 00).

Your task is to remove exactly one segment from the given sequence in such a way that the intersection of the remaining (n−1)(n−1)segments has the maximal possible length.

Input

The first line contains a single integer nn (2≤n≤3⋅1052≤n≤3⋅105) — the number of segments in the sequence.

Each of the next nn lines contains two integers lili and riri (0≤li≤ri≤1090≤li≤ri≤109) — the description of the ii-th segment.

Output

Print a single integer — the maximal possible length of the intersection of (n−1)(n−1) remaining segments after you remove exactly one segment from the sequence.

Examples

input

Copy

4
1 3
2 6
0 4
3 3

output

Copy

1

input

Copy

5
2 6
1 3
0 4
1 20
0 4

output

Copy

2

input

Copy

3
4 5
1 2
9 20

output

Copy

0

input

Copy

2
3 10
1 5

output

Copy

7

Note

In the first example you should remove the segment [3;3][3;3], the intersection will become [2;3][2;3] (length 11). Removing any other segment will result in the intersection [3;3][3;3] (length 00).

In the second example you should remove the segment [1;3][1;3] or segment [2;6][2;6], the intersection will become [2;4][2;4] (length 22) or [1;3][1;3](length 22), respectively. Removing any other segment will result in the intersection [2;3][2;3] (length 11).

In the third example the intersection will become an empty set no matter the segment you remove.

In the fourth example you will get the intersection [3;10][3;10] (length 77) if you remove the segment [1;5][1;5] or the intersection [1;5][1;5] (length 44) if you remove the segment [3;10][3;10].

題意：求刪除一個區間之後所有區間重複的最大長度，如果沒有重複就是0；

首先要求出所有區間的重複區域，然後一個邊一個邊的的刪除，然後找到最大的長度，這裡有貪心和暴力的思想，可以用陣列做，也可以用 multiset 庫函式做

//陣列
#include<bits/stdc++.h>
using namespace std;
const int MAXN=3*1e5+10;
multiset<int> sl;
multiset<int> sr;
struct NODE{
	int l;
	int r;
}node[MAXN];
int main(){
	int n;
	cin>>n;
	int a,b;
	for(int i=0;i<n;i++){
		cin>>a>>b;
		node[i].l=a;
		node[i].r=b;
		sl.insert(a);
		sr.insert(b);
	}
	int ans=0;
	for(int i=0;i<n;i++){
		sl.erase(sl.find(node[i].l));
		sr.erase(sr.find(node[i].r));
		int l=*sl.rbegin();
		int r=*sr.begin();
		ans=max(ans,r-l);
		sl.insert(node[i].l);
		sr.insert(node[i].r);
	}
	cout<<ans<<endl;
	return 0;
}

//multiset
#include<bits/stdc++.h>
using namespace std;
const int MAXN=3*1e5+10;
int l[MAXN];
int r[MAXN];
struct NODE{
	int l;
	int r;
}node[MAXN];
int main(){
	int n;
	cin>>n;
	for(int i=0;i<n;i++){
		cin>>node[i].l>>node[i].r;
		l[i]=node[i].l;
		r[i]=node[i].r;
	}
	int ans=0;
	sort(l,l+n);
	sort(r,r+n);
	for(int i=0;i<n;i++){
		int b=r[0];
		int a=l[n-1];
		
		if(node[i].l==a){
			a=l[n-2];
		}
		if(node[i].r==b){
			b=r[1];
		}
		ans=max(ans,b-a);
	}
	cout<<ans<<endl;
	return 0;
}