#include <iostream>
#include <fstream>
#include <deque>
#define nl '\n'

using namespace std;

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

const int NMAX = 5e6+1;

int n, k, v[NMAX];
long long int sum = 0;
deque<int> minis;

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