#include <iostream>
#include <fstream>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
int v[1001],i,n,d[1001],minim,k,s;
int main()
{
   fin>>n>>k;
   for(i=1;i<=n;i++)
        fin>>v[i];
    for(int p=1;p<=n-k+1;p++){
        d[p]=v[p];
        for(i=p+1;i<=p+k-1;i++)
           if(d[p]>v[i])
                d[p]=v[i];
    }
    s=0;
    for(i=1;i<=n-k+1;i++)
        s=s+d[i];
    fout<<s;
    return 0;
}