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

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

long long n,k,x,s;
deque<int> dq;
vector<int> sq;

int main()
{
    fin>>n>>k;
    for (int i = 1; i <= n; i++)
    {
        fin>>x;
        sq.push_back(x);
    }
    for (int i = 0; i < n; i++)
    {
        while (!dq.empty() && sq[dq.back()] >= sq[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front() <= i - k)
            dq.pop_front();
        if(i >= k - 1)
            s += sq[dq.front()];
    }
    fout<<s;
}