#include <iostream>
#include <fstream>
#include <deque>
#include <vector>

using namespace std;

int main() {
    
    ifstream f("deque.in");
    int n,k;
    f>>n>>k;
    vector<int>v;
    for(int i=0;i<n;i++)
    {
        int a;
        f>>a;
        v.push_back(a);
    }
    deque<int> deque1; 
    int sum = 0;

    for (int i = 0; i < v.size(); i++) {
        while (!deque1.empty() && v[deque1.back()] >= v[i]) {
            deque1.pop_back();
        }
        deque1.push_back(i);

        if (!deque1.empty() && deque1.front() <= i-k) {
            deque1.pop_front();
        }
        if (i>=k-1) {
            sum+=v[deque1.front()];
        }
    }

    ofstream g("deque.out");
    g<<sum;
    f.close();
    g.close();
    return 0;
}