#include <iostream>
#include <fstream>
#include <deque>

using namespace std;
long long n, k, suma = 0;
long long a[50000005];
deque<long long>Q;

void pushElement(long long x){
    while(!Q.empty() && a[Q.back()] > a[x])
        Q.pop_back();
    Q.push_back(x);
}

void peekElement(long long pos){
    while(!Q.empty() && pos - Q.front() > k)
        Q.pop_front();
}

void parcurgere(){
    for(long long i=0; i<k; ++i){
        pushElement(i);
    }
    for(long long i=k; i<n; ++i){
        peekElement(i);
        if(!Q.empty())
            suma += a[Q.front()];
        pushElement(i);
    }
    if(!Q.empty())
        suma += a[Q.front()];
}

int main()
{
    ifstream f("deque.in");
    f>>n>>k;
    for(long long i=0; i<n; ++i)
        f>>a[i];
    ofstream g("deque.out");
    parcurgere();
    g<<suma;
    return 0;
}