#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

int n, k, x, v[5000005];
long long int s=0;
deque<int> deq;



int main(){
    ifstream f("deque.in");
    f>>n>>k;
    for(int i=1;i<=n;i++)
        f>>v[i];
    for(int i=1;i<=n;i++)
    {
        while(deq.size() && v[deq.back()]>v[i])
            deq.pop_back();
        deq.push_back(i);
        if(deq.front()==i-k)
            deq.pop_front();
        if(i>=k)
            s+=v[deq.front()];
    }
    ofstream g("deque.out");
    g<<s;
    cout<<s;
    return 0;
}