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

ifstream fin("deque.in");
ofstream fout("deque.out");

int main()
{
	int min,s=0;
	int k,n;
	int a[],t=0;
	
	//citire n,k,vector[n];
	cin>>n;
	cin>>k;
	for(int i=0;i<n;i++)
		cin>>a[i];	

	//gasire minimi pentru fiecare 
	//subinterval de lungime k;
	for(i=t+1;i<k+t;i++)
	{
		a[t]=min;
		if(a[i]<min)
			a[i]=min;
		if(i=k+t-1)
		{ t++;
		  s=s+min;
		}
	}
	
	fout<<s;
	
	fin.close();
	fout.close();
	
}