#include <fstream>
#include <deque>
#include <climits>
using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");

deque < int > dq;
int n, k, a, s;
int main()
{
    cin>>n>>k;
    for(int i=1; i<=n; i++)
    {
        cin>>a;
        dq.push_front(a);
        if(i>=k)
        {
            int minim=INT_MAX;
            for(int j=0; j<k; j++)
            {
                int x=dq.at(j);
                if(x<minim)
                {
                    minim=x;
                }
            }
            s=s+minim;
            dq.pop_back();
        }
    }
    cout<<s;
    return 0;
}