#include <iostream>
#include <climits>
#include <fstream>
#include <deque>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
int v[5000005];
deque <int>dq;
int main()
{
    int n, k;
    long long sum = 0;
    in>>n>>k;
    for(int i = 1; i<=n; i++)
    {
        in>>v[i];
        if(!dq.empty() && dq.front() == i - k)
        {
            dq.pop_front();
        }
        while(!dq.empty() && v[i] < v[dq.back()])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(i >= k)
        {
            sum += v[dq.front()];
        }
    }
    out<<sum;
}