#include<fstream>
using namespace std;
ifstream f("transport.in");
ofstream g("transport.out");
long n,k,i,maxx,s,v[16001];
int main()
{
	f>>n>>k;
	for(i=1;i<=n;i++)
		f>>v[i];
	s=0;
	maxx=0;
	for(i=1;i<=n/k;i++)
	{	s=s+v[i];
		if(v[i]>maxx)
			maxx=v[i];
	}
	s=0;
	for(i=n/k+1;i<=(n/k)*2+1;i++)
	{	s=s+v[i];
		if(v[i]>maxx)
			maxx=v[i];
	}
	for(i=(n/k)*2+2;i<=n;i++)
	{	s=s+v[i];
		if(v[i]>maxx)
			maxx=v[i];
	}
	g<<maxx;
	f.close();
	g.close();
	return 0;
}