#include <iostream>
#include <fstream>
#include <vector>
#include <stdlib.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int k, n, i, j, mini, s, x, ck,cn;
 vector<int> v;
int main()
{

    f>>n>>k;
    cn=n;
   while(n)
   {
       f>>x;
       v.push_back(x);
       n--;
   }
    for(i=0; i<=cn-k; i++)
    {
        mini=v[i];
        for(j=i+1; j<i+k; j++)
        {
            if (v[j]<mini)
                mini=v[j];
        }
        s+=mini;

    }
    g<<s;
    return 0;

}