#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
#define MAX 5000100

deque <int> Q;
int a[MAX];

int main()
{
    int n, k, i;
    long long s = 0;
    fin >> n >> k;
    for(i = 1 ; i <= n ; i++)
    {
        fin >> a[i];
    }
    for(i = 1 ; i <= n ; i++)
    {
        while(Q.size() && a[i] < a[Q.front()])
            Q.pop_front();
        Q.push_front(i);
        if(Q.back() == i - k)
            Q.pop_back();
        if(i >= k)
        {
            s += a[Q.back()];
        }
    }
    fout << s << "\n";
}