#include <bits/stdc++.h>
#define ll long long
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    ll ans = 0;
    int n, k, x; fin >> n >> k;
    vector<int> v(n + 1);
    deque<int> dq;
    for (int i = 1; i <= n; i++) {
        fin >> v[i];
    }
    for (int i = 1; i <= n; i++) {
        while (!dq.empty() && v[dq.back()] >= v[i]) dq.pop_back();
        dq.push_back(i);
        if (dq.front() == i - k) dq.pop_front();
        if (i >= k) ans += v[dq.front()];
    }
    fout << ans;
    return 0;
}