//Ce stil am ;x
//Include
#include <stdio.h>
#include <limits.h>
#include <deque>
using namespace std;

//Variabile
FILE *in, *out;

int n, k;
int kminus1;
double suma;
int citit;

deque<int> d;
deque<int>::iterator it,d_end;

//Main
int main()
{
	in=fopen("deque.in","rt");
	out=fopen("deque.out","wt");
	fscanf(in, "%d%d",&n, &k);
	kminus1=k-1;
	for(int i=1;i<=kminus1;++i)
	{
		fscanf(in, "%d",&citit);
		d.push_back(citit);
	}
	
	for(int i=k;i<=n;++i)
	{
		fscanf(in, "%d",&citit);
		d.push_back(citit);
		int minim=INT_MAX;
		
		d_end=d.end();
		for(it=d.begin();it!=d_end;++it)
			if(*it<minim)
				minim=*it;
		
		suma+=(double)minim;
		d.pop_front();
	}
	
	fprintf(out, "%.0lf",suma);
	
	fclose(in);
	fclose(out);
	return 0;
}

//Ce stil am ;x