#include <fstream>
#include <set>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
const int nm=5000005;
int v[nm],n,k,s;
set<int>d;
int main()
{
    cin>>n>>k;
    for(int i=1;i<=n;i++)
        cin>>v[i];
    for(int i=1;i<=k;i++)
        d.insert(v[i]);
    for(int i=k+1;i<=n+1;i++)
    {
        s+=*d.begin();
        d.erase(v[i-k]);
        d.insert(v[i]);
    }
    cout<<"\n"<<s;
    return 0;
}