#include <iostream>
#include <fstream>
#include <queue>
using namespace std;
typedef pair<int,int> ii;
const int NMAX=5000000;
int v[NMAX+5];
deque <ii> q;
int main() {
	ifstream cin("deque.in");
	ofstream cout("deque.out");
	int n,k,i;
	long long s=0;
	cin>>n>>k;
	for(i=1;i<=n;i++) 
		cin>>v[i];
	for(i=1;i<=n;i++) {
		while(!q.empty() && q.back().first>=v[i])
			q.pop_back();
		q.push_back(ii(v[i],i));
		if(i>=k) {
			while(!q.empty() && i-q.front().second+1>k)
				q.pop_front();
			s+=q.front().first;}}
		cout<<s;
return 0;}