rt，n长度 5e7

#include <bits/stdc++.h>
using namespace std;
int nl[50000000],c;
void SWAP(int i,int j){
	int tmp=nl[j];
	nl[j]=nl[i];
	nl[i]=tmp;
}
void Fnd(int l,int r){
	if(l==r){
		printf("%d",nl[l]);
		return;
	}
	int i=l,j=r,k=nl[(l+r)/2];
	do{
		while(nl[j]>k)--j;
		while(nl[i]<k)++i;
		if(i<=j){SWAP(i,j);++i;--j;}
	}while(i<=j);
	if(c<=j)Fnd(l,j);
	else if(i<=c)Fnd(i,r);
	else Fnd(i+1,j-1);
}
int main(){
	int n;
	scanf("%d %d",&n,&c);
	for(int i=0;i<n;++i){
		scanf("%d",&nl[i]);
	}
	Fnd(0,n-1);
	return 0;
}