#include <iostream>
#include <fstream>
#include <climits>

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


int a[5000010];
int N,K;
long long s;
int main()
{
    int p,i,j,mini;
    fin>>n>>k;

    for(i=1;i<=n;i++)
        fin>>a[i];
    mini=INT_MAX;
    for(i=1;i<=N;i++)
    {
        if(a[i]<=mini)
        {
            mini=a[i];
            p=i;
        }
        if(p<=i-K)
        {
            mini=INT_MAX;
            p=0;
            for(j=0;j<K;j++)
            {
                if(a[i-j]<mini)
                {
                    mini=a[i-j];
                    p=i-j;
                }
            }
        }
        if(i>=K)
            s+=mini;
    }
    fout<<s;
    return 0;
}