#include<stdio.h>
#include<deque>
#define dim 5000100
using namespace std;

int a[dim],n,k;
long long int sum;
deque <int> q;
void read() 
{
	scanf("%d %d\n",&n,&k);
	for(int i=1 ; i<=n;i++)
		scanf("%d ",&a[i]);
}
void solve ()
{
	for(int i=1 ; i<=n;i++)
	{
		
		while (!q.empty() && a[i] <= a[ q.back() ])
		{
			q.pop_back();
		}
		q.push_back(i);
		
		if ( !q.empty() )	
		{	if ( q.front() == i-k ) 
				q.pop_front();
			if ( i >= k ) 
				sum+= a[ q.front() ] ;
		}
	}
	printf("%d\n",sum ) ;
}
int main ()
{
	freopen("deque.in","r",stdin);
	read ();
	freopen("deque.out","w",stdout);
	solve();
	return 0;
}