简单贪心

#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10;
int a[N],b[N];
bool cmp(int a,int b){return a>b;}
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);cout.tie(0);
	int n;cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	for(int i=1;i<n;i++)cin>>b[i];
	sort(a+1,a+n+1,cmp);sort(b+1,b+n,cmp);b[n]=-1;
	int ans=-1;
	for(int i=1,j=1;i<=n&&j<=n;i++,j++)
	{
		if(a[i]<=b[j])continue;
		if(ans!=-1){cout<<-1;return 0;}
		ans=a[i];j--;
	}
	cout<<ans;
	return 0;
}