#include <iostream>
#include <fstream>
#include <cmath>
#include <deque>
using namespace std;
 
ifstream fin("deque.in");
ofstream fout("deque.out");
 
const int MAX_SIZE = 5000005;
int v[MAX_SIZE];
 
int main() {
    int n, k;
    fin >> n >> k;
    for (int i = 1; i <= n; ++i) {
        fin >> v[i];
    }
    deque<pair<int, int>> minimums;
    long long sum = 0;
    for (int i = 1; i <= n + 1; ++i) {
        while (!minimums.empty() && minimums.back().first > v[i]) {
            minimums.pop_back();
        }
        if (i > k) {
            sum += minimums.front().first;
        }
        if (!minimums.empty() && i - k >= minimums.front().second) {
            minimums.pop_front();
        }
        minimums.push_back({v[i], i});
    
    }
    fout << sum;
}
 
/*
 
 1 1
 -1 -> -1
 
 5 1
 1 2 3 4 5 -> 15
 
 9 3
 -7 9 2 4 -1 5 6 7 1 -> -2
 
 9 3
 -7 9 2 4 -1 5 6 7 10 -> 3
 
 4 4
 1 -1 2 3 -> -1
 
 
 
 */