#include <iostream>
#include <algorithm>
#include <vector>
#include <stack>
#include <string>
#include <cmath>
#include <map>
#include <fstream>
#include <deque>

#define pb push_back
#define MAXN 1e9

using namespace std;

deque<int> deq;
vector<int> v;

ifstream f("deque.in");
ofstream g("deque.out");

int main() {
	int n, k;
	long long ans = 0;

	f >> n >> k;
	v.resize(n);
	for(int i = 0; i < n; i++)
		f >> v[i];
	for(int i = 0; i < n; i++) {
		while(deq.size() > 0 && v[deq.back()] >= v[i]) 
			deq.pop_back();
		deq.push_back(i);
		if(i >= k-1)
			ans += v[deq.front()];
		if(deq.size() > 0 && deq.front() == i-k+1)
			deq.pop_front();
	}

	g << ans << "\n";

	return 0;
}