#include <bits/stdc++.h>

using namespace std;
ifstream fin ("deque.in");
ofstream fout("deque.out");

deque < int > D;
int n , k , sum ;
int a[5000001];
int main()
{
    fin >> n >> k ;
    int x ;
    for ( int i = 1 ; i <= n ; i ++ )
        {
         fin >> a[ i ] ;
         while( D . empty() == false && a[D.back()] >= a[ i ] )
                D.pop_back();
         D.push_back( i );
         if( D.front() == i - k  )
            D.pop_front();
         if( i >= k )
            {
             sum += a[ D.front() ] ;
            }

        }
    fout<<sum;
    return 0;
}