///#include <iostream>
#include "fstream"
#include <deque>

using namespace std ;

ifstream cin ("deque.in") ;
ofstream cout ("deque.out") ;

int n, k ;
int v[5000005] ;
deque < int > D ;

int main()
{

    long long ans = 0 ;

    cin >> n >> k ;

    for (int i = 1 ; i <= n ; i ++)
    {

        cin >> v[i] ;

        while (!D.empty() && v[i] <= v[D.back()])
            D.pop_back() ;

        D.push_back(i) ;

        if (D.front() == i - k)
            D.pop_front() ;

        if (i >= k)
            ans += v[D.front()] ;


    }

    cout << ans ;

    return 0 ;

}