#include <iostream>
#include <fstream>
using namespace std;
#define maxn 5000010
int v[maxn], deq[maxn];

int main()
{
    int n, k;
    long long sum = 0;
    ifstream f("deque.in");
    ofstream g("deque.out");
    f>>n>> k;
    for (int i=0; i<n; i++)
        f>>v[i];
    int left = 0;
    int right = -1;
    for (int i = 0; i < n; i++)
    {
        if (deq[left] <= i - k)
            left++;
        while (left <= right && v[deq[right]] >= v[i])
            right--;
        deq[++right] = i;
        if (i+1 >= k)
            sum += v[deq[left]];
    }
    g<<sum;
}