#include <iostream>
#include <fstream>

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

int a[101],n,i,k,minn=1000000001,s,j;

int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++)
        f>a[i];
    for(i=1;i<=n && i+1-k<=n;i++)
    {
        for(j=i;j<=k+i-1;j++)
            if(a[j]<minn)
                minn=a[j];
        s=s+minn;
        minn=1000000001;
    }
    g<<s;
    return 0;
}