#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque<int>d;
long long a[5000005];
int main() {

    int n, k;
    fin>>n>> k;
    for(int i=1; i<=n; i++)
        fin>>a[i];
    long long s=0;
    for(int i=1; i<=n; i++) {
        while (!d.empty() && a[d.back()]>=a[i]) d.pop_back();
            d.push_back(i);
        if (d.front()<=i-k)
            d.pop_front();
        if (i>=k)
            s+=a[d.front()];
    }
    fout<<s;
    return 0;
}