#include <bits/stdc++.h>
#define ll long long int
using namespace std;
deque <ll> q;
const int nmax=1e6;
ll arr[5*nmax+5],n,k,sum=0;
void printKMax(ll arr[], ll n, ll k)
{

    // Create a Double Ended Queue,
    // Qi that will store indexes
    // of array elements
    // The queue will store indexes
    // of useful elements in every
    // window and it will
    // maintain decreasing order of
    // values from front to rear in Qi, i.e.,
    // arr[Qi.front[]] to arr[Qi.rear()]
    // are sorted in decreasing order
    std::deque<int> Qi(k);

    /* Process first k (or first window)
     elements of array */
    int i;
    for (i = 0; i < k; ++i)
    {

        // For every element, the previous
        // smaller elements are useless so
        // remove them from Qi
        while ((!Qi.empty()) && arr[i] >=
                            arr[Qi.back()])

             // Remove from rear
            Qi.pop_back();

        // Add new element at rear of queue
        Qi.push_back(i);
    }

    // Process rest of the elements,
    // i.e., from arr[k] to arr[n-1]
    for (; i < n; ++i)
    {

        // The element at the front of
        // the queue is the largest element of
        // previous window, so print it
        cout << arr[Qi.front()] << " ";

        // Remove the elements which
        // are out of this window
        while ((!Qi.empty()) && Qi.front() <=
                                           i - k)

            // Remove from front of queue
            Qi.pop_front();

        // Remove all elements
        // smaller than the currently
        // being added element (remove
        // useless elements)
        while ((!Qi.empty()) && arr[i] >=
                             arr[Qi.back()])
            Qi.pop_back();

        // Add current element at the rear of Qi
        Qi.push_back(i);
    }

    // Print the maximum element
    // of last window
    cout << arr[Qi.front()];
}
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin>>n>>k;
    for(int i=0;i<n;++i)
        cin>>arr[i];
    int i;
    for(i=0;i<k;++i){
        while((!q.empty()) && arr[i]<=arr[q.back()])
            q.pop_back();
        q.push_back(i);
    }
    for(;i<n;++i){
        sum+=arr[q.front()];
        while((!q.empty()) && q.front()<=i-k)
            q.pop_front();
        while((!q.empty()) && arr[i]<=arr[q.back()])
            q.pop_back();
        q.push_back(i);
    }
    sum+=arr[q.front()];
    cout<<sum;
}