#include <bits/stdc++.h>

using namespace std;

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

int main() {
    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) {
            while(!q.empty() && q.front() == i - k) q.pop_front();
            s += a[q.front()];
        } 
    }
    fout << s;

    return 0;
}