WA了#6

#include<bits/stdc++.h>
using namespace std;
long long n,l[1000010],r[1000010],ans;
deque<long long>p;
int main(){
	cin>>n;
	if(n==1){
		cin>>l[1]>>r[1];
		cout<<1;
		return 0;
	}
	for(int i=1;i<=n;i++){
		cin>>l[i]>>r[i];
		while(p.size()&&r[i]<l[p.front()])p.pop_front();
		if(p.size())ans=max(ans,i+1-p.front());
		int k=i;
		while(p.size()&&l[i]>l[p.back()]){
			k=p.back();
			p.pop_back();
		}
		l[k]=l[i];
		p.push_back(k);
	}
	cout<<ans;
}