//#include <iostream>
#include <fstream>
using namespace std;
long long n,a[5000005],i,mn,s,j,k;
ifstream cin("deque.in");
ofstream cout("deque.out");
int main()
{
    cin>>n>>k;
    for(i=1;i<=n;i++)
        cin>>a[i];
    for(i=1;i<=n;i++)
    {
        mn=10000000;
        for(j=i;j<i+k;j++)
        {
            if(a[j]<mn)
            {
                mn=a[j];
               // cout<<mn<<" ";
            }

        }
        //cout<<mn<<" ";
        s=s+mn;
    }
    cout<<s;
    return 0;
}