#include <iostream>
#include <fstream>
#include <vector>


int st = 0, dr = 0, v[5000001], deq[5000001];



std::ifstream in("deque.in");
std::ofstream out("deque.out");

long long int s = 0;

void print()
{
    out << s;
}

int main()
{
    int n, k;
    in >> n >> k;

    for (int i = 1; i <= n; i++)
        in >> v[i];

    for (int i = 1; i <= n; i++)
    {
        while (v[i] <= v[deq[dr]] && st <= dr)
            dr--;

        dr++;
        deq[dr] = i;

        if (k - i < 1 - deq[st])
            st++;

        if (i >= k)
            s += v[deq[st]];
    }

    print();

    return 0;
}