#include<stdio.h>
#include<list>
int main()
{
    FILE *fin,*fout;
    fin=fopen("deque.in","r");
    fout=fopen("deque.out","w");
    long int n,k,s=0,t,min=10000000;
    std::list<int> a;
    std::list<int>::iterator j;
    fscanf(fin,"%ld %ld",&n,&k);
    for(int i=0;i<k;i++)
    {
            fscanf(fin,"%ld",&t);
            a.push_back(t);
    }
    n-=k;
    for(j=a.begin();j!=a.end();j++)
    {
                                   //fprintf(fout,"%ld %ld \n",min,*j);
                                   if(min>*j)
                                   {
                                             min=*j;
                                   }
    }
    s+=min;
    for(int i=0;i<n;i++)
    {
            fscanf(fin,"%ld",&t);
            a.push_back(t);
            a.pop_front();
            min=10000000;
            for(j=a.begin();j!=a.end();j++)
            {
                                           if(min>*j)
                                           {
                                                     min=*j;
                                           }
            }
            s+=min;
    }
    fprintf(fout,"%ld",s);
}