#include <iostream>
#include <fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int a[5000010],n,k,head,tail,x,ind[5000010],sum;
void solve()
{
    f>>n>>k;head=1;tail=0;
    for(int i=1;i<=n;++i)
    {
        f>>x;
        while(head<=tail&&x<=a[tail])tail--;
        a[++tail]=x;ind[tail]=i;
        if(ind[head]==i-k)head++;
        if(i>=k)sum+=a[head];
    }
    g<<sum;
}
int main()
{
    solve();
    return 0;
}