#include <fstream>
#include <set>
using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

std :: multiset <int> myset;
std :: multiset <int> :: iterator it;

int first,n,k,fi,i,x,suma;

int main ()
{
    f>>n>>k;
    f>>fi;
    myset.insert(fi);
    for (i=2;i<=k;i++)
    {
        f>>x;
        myset.insert(x);
    }

it=myset.begin();
suma+=*it;

    myset.erase(myset.find(fi));

    for (i=1;i<=n-k+1;i++)
    {
        f>>x;
        myset.insert(x);
        it=myset.begin();
        suma+=*it;
        myset.erase(myset.find(x));
    }

g<<suma<<'\n';
return 0;
}