#include <bits/stdc++.h>

using namespace std;

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

int main() {
    ios_base::sync_with_stdio(false);
    fin.tie(NULL);
    fin >> n >> k;
    for(i = 1; i <= n; i++) fin >> a[i];
    for(i = 1; i <= n; i++) {
        while(!q.empty() && a[i] <= a[q.back()]) q.pop_back();
        q.push_back(i);
        if(i >= k) {
            if(!q.empty() && q.front() == i - k) q.pop_front();
            r += a[q.front()];
        }
    }
    fout << r;

    return 0;
}