#include <fstream>
#include <deque>
#include <algorithm>
using namespace std;

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

const int NMAX = 5e6 + 5;
int a[NMAX],n, k;

int main()
{
    fin >> n >> k;
    for(int i = 1; i <= n; i++)
        fin >> a[i];

    long long sum = 0;
    deque<int> minQ;
    for(int i = 1; i <= n; i++)
    {
        while(!minQ.empty() && a[i] <= a[minQ.back()])
            minQ.pop_back();
        minQ.push_back(i);

        if(minQ.front() == i - k)
            minQ.pop_front();

        if(i >= k)
            sum += 1LL * a[minQ.front()];
    }
    fout << sum;

    return 0;
}