#include <bits/stdc++.h>

using namespace std;

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

long long suma,n,k;
long long v[5000001];
unsigned int mem=1;
deque <int> dq;


int main(){
	fin>>n>>k;
	for(int i = 1; i<=n; i++)
		fin>>v[i];
	dq.push_back(1);
	for(int i = 2;i<=n;i++){
		while(!dq.empty() && v[i]<=v[dq.back()])
			dq.pop_back();
		dq.push_back(i);
		if(i-dq.front()==k)
			dq.pop_front();
		if(i>=k)
			suma+=v[dq.front()];
	
	}
	fout<<suma;
	return 0;
}