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

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

    int N, K;
    fin >> N >> K;
    vector<int> A(N);
    for (int i = 0; i < N; ++i) {
        fin >> A[i];
    }

    deque<int> dq; 
    long long suma = 0;

    for (int i = 0; i < N; ++i) {
        if (!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 - 1) {
            suma += A[dq.front()];
        }
    }

    fout << suma << "\n";

    return 0;
}