#include <fstream>
#include <queue>
using namespace std;

ifstream fin ("deque.in");
ofstream fout ("deque.out");
int n, k, v[5000001], s;

deque <int> dq; //aici punem doar pozitiile din vector

int main(){
    int i, minim;
    fin >> n >> k;
    for (i = 1; i<= n; i++)
        fin >> v[i];
    for(i = 1; i<= n; i++)
    //adaugam nou element
    {
        while(v[dq.front()] > v[i] && dq.empty()!=1)
        {
            dq.pop_front();
            dq.push_front(i)
        }
        if(i > k)
        {
            if (dq.begin() < i-k+1) //nu este in ultimele k elemente
                dq.pop_back();
            minim = v[dq.begin()];
            s += minim;
        }
    }

    fout<<s;
    return 0;   
}