#include <bits/stdc++.h>
#define MAXN 5000000
#define LL long long

using namespace std;

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

int n, k, arr[MAXN + 1];
LL sum = 0;
deque<int> minime;
int main() {
    fin >> n >> k;
    for (int i = 1; i <= n; i++)
        fin >> arr[i];
    for (int i = 1; i <= n; i++) {
        while (minime.size() && arr[i] <= arr[minime.back()])
            minime.pop_back();
        minime.push_back(i);
        if (minime.front() == i - k)
            minime.pop_front();
        if (i >= k)
            sum += arr[minime.front()];
    }

    fout << sum;
    return 0;
}