#include <bits/stdc++.h>

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

int main() {
    int n, k;
    fin >> n >> k;

    std::deque<int> dq;
    int sum = 0;

    std::vector<int> A(n);
    for(int i = 0; i < n; ++i) {
        fin >> A[i];
    }

    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) {
            sum += A[dq.back()];
        }
    }

    fout << sum;
    return 0;
}