#include <iostream>
#include <vector>
#include <fstream>
using namespace std;

int main(){
    vector < int > sir;
    vector < int > minime;
    int minim_global = 0;
    int n, k;
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin >> n >> k;
    for( int i = 0; i < n; i++ ){
        int minim_local = 5000000;
        int numar;
        fin >> numar;
        if( sir.size() < k ){
            sir.push_back(numar);
            if( sir.size() == k ){
                for( int j = 0; j < k; j++ ){
                    if( sir[j] < minim_local ) minim_local = sir[j];
                }
                minim_global += minim_local;
            }
        }
        else{
            sir.push_back(numar);
            for( int j = 0; j < k; j++ ){
                sir[j] = sir[j+1];
                if( sir[j] < minim_local ) minim_local = sir[j];
            }
            sir.pop_back();
            minim_global += minim_local;
        }
    }
    fout << minim_global;
}