#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n, k, x;
long long rez;
deque <pair <int, int>> dq;

int main()
{
    f >> n >> k;
    for(int i=1; i<=n; i++)
    {
        f >> x;
        while(!dq.empty() && dq.front().second <= i-k)
            dq.pop_front();
        while(!dq.empty() && x <= dq.back().first)
            dq.pop_back();
        dq.push_back({x, i});
        if(i >= k)
            rez += dq.front().first;
    }
    g << rez;
}