#include <iostream>
#include <fstream>
#include <deque>
using namespace std;


long long n, k, i, r, a[5000002];
deque<int> q;

int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    cin >> n >> k;
    for(i = 1; i <= n; i++)
        cin >> a[i];
    for(i = 1; i <= n; i++)
    {
        while(!q.empty() && a[i] <= a[q.back()]) q.pop_back();
        q.push_back(i);
        if(i >= k)
        {
            if(!q.empty() && q.front() == i - k) q.pop_front();
            r += a[q.front()];
        }
    }
    cout << r;
    return 0;
}