#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque<int>e;
   int main()
   {   int i,j,n,k,v[5000010],suma=0;
       f>>n>>k;
       for(i=1;i<=n;i++)f>>v[i];
       for(i=1;i<=n-k+1;i++)
       {   int min=INT_MAX;
             for(j=i;j<=k+i-1;j++)
             {if(v[j]<min)min=v[j];}
             e.push_front(min);}

      while(!e.empty())
      {   suma+=e.front();
          e.pop_front();}
      g<<suma;
      f.close();
      g.close();
       return 0;
   }