//de schimbat MAX
#include <iostream>
#include <deque>
#include <stdio.h>

using namespace std;

#define MAX 50000//00

int main()
{
    FILE *fin = fopen("deque.in", "r"), *fout = fopen("deque.out", "w");

    int N, K, n, v[MAX], minime[MAX];
    //v are numere si minime are indici
    //dq are tot indici
    long long sum = 0;

    fscanf(fin, "%d %d", &N, &K);
    deque<int> dq;

    for (int i = 0; i < N; i ++) {
        fscanf(fin, "%d", &n);
        v[i] = n;
    }

    //minimul e in back

    for(int i = 0; i < N; i++) {
        //cat timp minimul e in afara intervalului scoate-l
        while (!dq.empty() && dq.back() <= i - K) {
            dq.pop_back();
        }

        //scoate toate maximele mai mari decat curentul
        //nu vor fi niciodata minime
        while (!dq.empty() && v[dq.front()] > v[i]) {
            dq.pop_front();
        }

        dq.push_front(i);

        minime[i] = dq.back();
    }

    for (int i = K - 1; i < N; i++) {
        sum += v[minime[i]];
    }

    fprintf(fout, "%d", sum);

    return 0;
}