/*
ID: mihai_a3
PROG: humble
LANG: C++
*/

#include <fstream>
#include <algorithm>
using namespace std;

const int N=1000005,inf=2000000;
int v[103],sol[N],n,m;

ifstream in("humble.in");
ofstream out("humble.out");

void bkt(int p,long long val)
{
	if (p==n+1)
	{
		if (sol[0]<N-2)
		sol[++sol[0]]=(int)val;
		return;
	}
	while (val<=inf)
	{
		bkt(p+1,val);
		val*=v[p];
	}
}

int main()
{
	in>>n>>m;
	for (int i=1;i<=n;i++)
		in>>v[i];
	bkt(1,1);
	sort(sol+1,sol+sol[0]+1);
	out<<sol[m+1]<<"\n";
	return 0;
}