求助

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
long long int n,k,a[1000000];
int main()
{
    cin>>n>>k;
    for(int i=0;i<=n;++i)
    {
        cin>>a[i];
    }
    nth_element(a,a+k,a+n);
    cout<<a[k]<<endl;
    return 0;
}