#include<iostream>
#include<fstream>
#include<deque>
using namespace std;
deque<int> q;
int x[5000001],k,n;
long long s;
int main()
{ifstream f("deque.in");
ofstream h("deque.out");
int i;
f>>n>>k;
for(i=1;i<=n;i++)
	f>>x[i];
for(i=1;i<=n;i++)
{while(q.size()&&x[i]<x[q.back()])
	q.pop_back();
	q.push_back(i);
	if(q.front()==i-k)
		q.pop_front();	
if(i>=k)
s+=x[q.front()];
}
h<<s;

	return 0;}