#include <fstream>
#include <deque>
#include <climits>
using namespace std;


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


deque<int>c;
int n,i,K,s,v[5000001],minim=INT_MAX;
int main()
{
   f>>n>>K;
   for(i=1;i<=n;i++)
   f>>v[i];

   for(i=1;i<=K;i++)
   {
       c.push_back(v[i]);
       if(v[i]<minim)minim=v[i];
   }
   s+=minim;

   for(i=K+1;i<=n;i++)
   {
       while(c.size()>=K){c.pop_front();}
       while(!c.empty()&&c.front()>=v[i])c.pop_front();
       c.push_back(v[i]);

       s+=c.front();

   }
   g<<s;
    return 0;
}