#include <iostream>
#include <fstream>

using namespace std;

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

int v[5000001], dq[5000001];

int main() {

    int n, k, st=0, dr=0;
    long long s = 0;

    fin >> n >> k;
    for (int i = 1; i <= n; i++)
        fin >> v[i];

    for (int i = 1; i <= n; i++) {
        while (st <= dr && v[i] <= v[dq[dr]] )dr--;
        dr++;
        dq[dr] = i;
        if (k - i < 1 - dq[st])st++;
        if (i >= k)s += v[dq[st]];
    }

    fout << s;

    return 0;
}