#include <iostream>
#include <fstream>
#include <deque>
#include <set>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

int a[5000005], q[5000005];
int p, u;
long long int rez;
int n, k;

int main()
{
    f >> n >> k;
    p = 1, u = 0;
    for (int i = 1;i <= n;i++)f >> a[i];
    for (int i = 1;i <= n;i++){
        while(p <= u && a[i] <= a[q[u]])u--;
        q[++u] = i;
        if (q[p] == i - k)p++;
        if (i >= k)rez += a[q[p]];
    }
    g << rez;
}