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

using namespace std;

long long f(int N, int K, const vector<int>&t) {
    deque<int> deq;
    long long ossz= 0;
    for (int i = 0; i < N; ++i) {
        if (!deq.empty() && deq.front() == i - K) {
            deq.pop_front();
        }
        while (!deq.empty() && t[deq.back()] > t[i]) {
            deq.pop_back();
        }
        deq.push_back(i);
        if (i >= K - 1) {
            ossz+=t[deq.front()];
        }
    }
    return ossz;
}

int main() {
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    int N,K;
    fin >> N >> K;
    vector<int>t(N);
    for (int i = 0; i < N; ++i) {
        fin >>t[i];
    }
    fout<<f(N, K,t);
    return 0;
}