#include<fstream>
#include<algorithm>
using namespace std;

int d[5000000],a[5000000];
int pr,ult,i,minim,s;
int k,n,j;

int main ()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin>>n>>k;
    for (i=1;i<=n;i++)
        fin>>a[i];
    for (i=1;i<=k;i++)
        d[i]=a[i];
    pr=1; ult=k; s=0;
    for (i=k+1;i<=n+1;i++)
    {
        minim=d[pr];
        for (j=pr+1;j<=ult;j++)
            minim=min(minim,d[j]);
        s+=minim;
        pr++; ult++;
        d[ult]=a[i];
    }

    fout<<s<<"\n";
    fin.close();
    fout.close();
    return 0;
}