#include <bits/stdc++.h>

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");
int n, i, k, s, a[5000002];
deque<int> q;

int main() {
    ios_base::sync_with_stdio(false);
    fin.tie(nullptr);
    fout.tie(nullptr);

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

    for(i = 1; i <= n; i++) {
        while(!q.empty() && a[q.back()] >= a[i]) q.pop_back();
        q.push_back(i);

        if(q.front() == i - k) q.pop_front();
        if(i >= k) s += a[q.front()];
    }
    fout << s;

    return 0;
}