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

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

deque<int> deq;
int v[5000010];
int n, k;
long long s;

int main()
{
    fin >> n >> k;
    for(int i = 1; i <= n; i++) fin >> v[i];
    for(int i = 1; i <= n; i++)
    {
        while(!deq.empty() && v[i] <= v[deq.back()]) deq.pop_back();
        deq.push_back(i);

        if(!deq.empty() && deq.front() == i - k) deq.pop_front();
        if(i >= k) s += v[deq.front()];
    }
    fout << s;
}