#include <bits/stdc++.h>
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

int n, k;
deque<pair<int, int>> dq;
int main() {
    fin >> n >> k;
    int sum = 0;
    for(int i = 1; i <= n; i++)
    {
        int x, min;
        fin >> x;
        while(!dq.empty() && i - dq.front().second + 1 > k)
        {
            dq.pop_front();
        }
        while(!dq.empty() && dq.back().first >= x)
        {
            dq.pop_back();
        }
        if(dq.empty())
        {
            min = x;
        }
        else{
            min = dq.front().first;
        }
        if(i >= k)
        {
            sum += min;
        }
        
        dq.push_back({x, i});
    }
    fout << sum;
    return 0;
}