#include <fstream>
#include <set>
#include <deque>
#include <iostream>

using namespace std;

int main() {
    ifstream in("deque.in");
    ofstream out("deque.out");

    int n, k;
    in>>n>>k;
    multiset<int> m;
    deque<int> d;
    for(int i=0;i<k;i++)
    {
        int x;
        in>>x;
        m.insert(x);
        d.push_back(x);
    }

    long long s=*m.begin();
    for(int i=k;i<n;i++)
    {
        int x;
        in>>x;
        m.erase(m.find(d.front()));
        m.insert(x);
        d.pop_front();
        d.push_back(x);
        s+=*m.begin();
    }

    out<<s;
    return 0;
}