#include <fstream>
using namespace std;

ifstream cin ("deque.in");
ofstream cout ("deque.out");

int v[5000001];
int codat[5000000];
int main()
{
    int n,k;
    cin >>n>>k;
    int dr = 0;
    int st = 1;
    long long s = 0;
    for (int i = 1; i <= n; i++)
    {
        cin >>v[i];
        while (st <= dr && v[i] < v[codat[dr]])
            dr--;
        dr++;
        codat[dr] = i;
        if (i >= k)
        {
            if (i - codat[st] + 1 > k)
                st++;
            s += v[codat[st]];
        }
    }
    cout <<s;
    return 0;
}