#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
long long n, a[5000010], i, k, s;
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 (Q.front() == i-k) Q.pop_front();
        if (i >= k) s+= a[Q.front()];
    }
    fout << s;
    return 0;
}