#include <iostream>
#include <deque>
#include <fstream>
using namespace std;
long long A[10000000];  

int main() {
   ifstream fin("deque.in");
   ofstream fout("deque.out");
    int N, K;
    fin >> N >> K;

    for (int i = 0; i < N; i++)
        fin >> A[i];

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

    for (int i = 0; i < N; i++) {


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

        dq.push_back(i);


        if (dq.front() <= i - K)
            dq.pop_front();

     
        if (i >= K - 1)
            sum += A[dq.front()];
    }

    fout << sum;
    return 0;
}