#include<fstream>
#include<deque>
#include<iostream>
#include<vector>
#include<cstdlib>

using namespace std;

ofstream g("deque.out");

deque <int> Q;
int n, k, pos;
long long s;
int V[5000005];
char Buffer[20000000];
int const Buffer_Size = 20000000;

void citeste(int & nr)
{
    int negativ = 0;
    nr = 0;
    while((Buffer[pos] < '0' || Buffer[pos] > '9') && Buffer[pos]!='-')
        pos++;
    if(Buffer[pos] == '-'){
        negativ = 1;
        pos++;
    }
    while(Buffer[pos] >= '0' && Buffer[pos] <= '9')
        nr = nr*10 + Buffer[pos++] - '0';

    if(negativ)
        nr = -nr;
}

void citire()
{
    freopen("deque.in", "r", stdin);
    fread(Buffer, 1, Buffer_Size, stdin);

    citeste(n); citeste(k);
    for(int i=1; i<=n; i++){
        citeste(V[i]);
    }
}

void rez()
{
    int i;

    Q.push_back(1);
    for(i=2; i<=n; i++){
        if(Q.front() == i - k)
            Q.pop_front();
        if(Q.size())
            while((V[Q.back()] >= V[i])){
                Q.pop_back();
                if(Q.empty())
                    break;
            }

        Q.push_back(i);

        if(i >= k)
            s += V[Q.front()];
    }

    g<<s<<"\n";
}

int main()
{
    citire();
    rez();
    return 0;
}