#include <iostream>
#include <fstream>

#define NMax 5000001

using namespace std;

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

int v[NMax];

int main()
{
    int n,k,i,j,S=0,min;
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>v[i];
    for(i=1;i<=n;i++)
    {
        min=10000001;
        for(j=i;j<=k+i-1;j++)
            if(v[j]<min)
                min=v[j];
        S+=min;
    }
    fout<<S;
    fin.close();
    fout.close();
    return 0;
}