#include <fstream>
#include <algorithm>
#include <deque>

std::ifstream fin;
std::ofstream fout;

int main ()
{
    int n;
    int k;
    fin.open("deque.in");
    fin >> n >> k;
    std::deque <int> Q;
    const int Inf = 0x3f3f3f3f;
    int minim {Inf};
    int s(0);
    while (n --)
    {
        int x;
        fin >> x;
        Q.push_back(x);
        if (Q.size() == k)
        {
            minim = Inf;
            for (auto y : Q)
                if (y < minim)
                    minim = y;
            s += minim;
            Q.pop_front();
        }
    }
    fin.close();
    fout.open("deque.out");
    fout << s;
    fout.close();
    return 0;
}