#include<bits/stdc++.h>
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

vector<int> A;
deque<int> dq;

int main() {
    int N, K, i;
    fin >> N >> K;

    A.resize(N+1);
    for (int i = 1; i <= N; ++i) {
        fin >> A[i];
    }


    long long sum = 0;

    for (i = 1; i <= N; ++i) {
        while (!dq.empty() && dq.front() < i - K + 1) {
            dq.pop_front();
        }

        while (!dq.empty() && A[dq.back()] >= A[i]) {
            dq.pop_back();
        }

        dq.push_back(i);

        if (i >= K) {
            sum += A[dq.front()];
        }
    }

    fout << sum << endl;

    return 0;
}