#include <fstream>
using namespace std;

int main(){
	unsigned long n,k,x;
	ifstream f("sdo.in");
	f>>n>>k;
	bool *v=new bool[n];
	for(unsigned i=0;i<n;i++){
		f>>x;
		v[x]=0;
	}
	f.close();
	ofstream g("sdo.out");
	x=0;
	for(unsigned long i=0;i<n;i++)
		if(!v[i]){
			x++;
			if(x==k){
				g<<i;
				break;
			}
		}
	g.close();
	return 0;
}