nth_element 牛皮

#include <bits/stdc++.h>
using namespace std;
int a[10000010]; 
int main(){
	int n,k;
	cin>>n>>k; 
	for(int i=1;i<=n;i++)scanf("%d",&a[i]);
	nth_element(a+1,a+k+1,a+n+1);
	cout<<a[k+1];
	return 0;
}