就是用的离散化呀

#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=3e4+15;
int a[N],b[N],n,tmp[N],tmp1[N];
signed main()
{
	cin>>n;
	for(int i=1;i<=n;i++) cin>>a[i]>>b[i],tmp[i]=a[i],tmp1[i]=b[i];
	sort(tmp+1,tmp+1+n);
	sort(tmp1+1,tmp1+1+n);
	int len=unique(tmp+1,tmp+1+n)-(tmp+1),len1=unique(tmp1+1,tmp1+1+n)-(tmp1+1);
	cout<<tmp1[len1]-tmp[1]<<endl;
	return 0;
}