#include <stdio.h>
#include <fstream>
#include <deque>

using namespace std;

int n;
int k;
int a[5000100];

deque <int> b;

void citire()
{
    ifstream fin("deque.in");
    fin>>n>>k;
    for(int i=0;i<n;i++)
        fin>>a[i];
}

void ceva()
{
    long long s=0;
    for(int i=0;i<n;i++)
    {
        while(!b.empty() && a[i]<a[b.back()])
        {
            b.pop_back();
        }
        b.push_back(i);
        if(b.front()<=i-k)
            b.pop_front();
        if(i>=k-1)
            s+=a[b.front()];
    }
    printf("%lld\n",s);
}

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    citire();
    ceva();

    return 0;
}