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

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

int n, k, aux, s, minim;
std::deque<int> coada;

int main(int argc, char *argv[]){
    fin >> n >> k;
    for (int i = 0; i < k; i++){
        fin >> aux;
        coada.push_back(aux);
    }
    minim = 10000000;
    for (int i = 0; i < k; i++)
        if (coada[i] <= minim)
            minim = coada[i];
    s+=minim;
    for (int i = 0; i < n - k; i++){
        minim = 10000000;
        coada.pop_front();
        fin >> aux;
        coada.push_back(aux);
        for (int i = 0; i < k; i++)
            if (coada[i] <= minim)
                minim = coada[i];
        s+= minim;
    }
    fout << s;
    return 0;
}