#include <bits/stdc++.h>
using namespace std;

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

int main() {
    int arraySize, sequenceSize;
    fin >> arraySize >> sequenceSize;
    vector<int> arr(arraySize);
    for (int i = 0; i < arraySize; ++i) {
        fin >> arr[i];
    }
    long long sum = 0;
    vector<int> dq(arraySize);
    int front = 0, back = -1;
    for (int i = 0; i < arraySize; ++i) {
        while (front <= back && dq[front] <= i - sequenceSize) {
            ++front;
        }
        while (front <= back && arr[dq[back]] >= arr[i]) {
            --back;
        }
        dq[++back] = i;
        if (i >= sequenceSize - 1) {
            sum += arr[dq[front]];
        }
    }
    fout << sum;
    return 0;
}