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

long long v[50000005];

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