#include <fstream>

int main()
{
    std::ifstream f("deque.in");
    int N, K, Minim, Suma;
    f >> N >> K;
    int deq[K];

    f >> Minim;
    deq[0] = Minim;
    for(int i = 1; i < K; ++i)
    {
        f >> deq[i];
        if(deq[i] < Minim)
            Minim = deq[i];
    }
    Suma = Minim;

    unsigned poz = 0;
    while(f >> deq[poz])
    {
        Minim = deq[poz];
        for(int i = 0; i < K; ++i)
            if(deq[i] < Minim)
                Minim = deq[i];

        Suma += Minim;
        ++poz %= K;
    }

    std::ofstream g("deque.out");
    g << Suma;
    return 0;
}