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

int main() {
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin.tie(0);
    std::ios_base::sync_with_stdio(0);
    const int MAX_N = 5000000;
    int v[MAX_N], dq[MAX_N];
    int n, k, frnt = 1, bck = 0;
    long long sumMins = 0;
    fin >> n >> k;
    for (int i = 0; i < n; ++i) {
        fin >> v[i];
    }
    for (int i = 0; i < n; ++i) {
        while (frnt <= bck && v[i] <= v[dq[bck]]) {
            --bck;
        }
        dq[++bck] = i;
        if (dq[frnt] == i - k) {
            ++frnt;
        }
        if (i + 1 >= k) {
            sumMins += v[dq[frnt]];
        }
    }
    fout << sumMins;
}