#include <fstream>
#include <deque>

using namespace std;

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

long long int vect[5000001] , suma_min ;
unsigned long k , n , i ;

int main()
{
    fin >> n >> k ;

    deque <int> d ;

    for ( i = 1 ; i <= n ; i ++ )
    {
        fin >> vect[i] ;
    }

    for ( i = 1 ; i <= n ; i ++ )
    {
        while ( d.empty() == 0 && vect[i] <= vect[d.back()] )
        {
            d.pop_back() ;
        }

        d.push_back(i) ;

        if ( d.front() == i - k )
        {
            d.pop_front() ;
        }

        if ( i >= k )
        {
            suma_min += vect[d.front()] ;
        }
    }

    fout << suma_min ;

    return 0;
}