#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream cin("deque.in") ;
ofstream cout("deque.out") ;
    int n,k,a[5000005],i,s,b[5000005],h=1,t=0;
    cin>>n ;
    cin>>k ;
    for (i=1;i<=n;i++) ;

cin>>a[i];
    cin.close() ;
  for(i=1;i<=n;i++)
{
while(h<=t&&a[i]<=a[b[t]])
t--;
b[++t]=i;
if(b[h]==i-k)
h++;
if(i>=k)
s+=a[b[h]];}
cout<<s;
cout.close() ;
}