#include<bits/stdc++.h>

using namespace std;

deque<int> d;
long long sum , a[5000005] ;

int main(){
    ifstream in("deque.in");
    ofstream out("deque.out");
    int n , k ;
    in >> n >> k;
    for(int i = 1 ; i <= n ; i++)
        in >> a[i];

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

        while(!d.empty() && a[i] <= a[d.back()])
            d.pop_back();

        d.push_back(i);

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

        if(i >= k){
            sum += a[d.front()];

        }
    }

    out << sum ;

}