#include <fstream>
#include <set>
#include <utility>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
long long n, i, x[5000010], S, k;

set< pair<long long, long long> > s;
pair<long long, long long> p;
set< pair<long long, long long> >::iterator it;

int main(){
    f>>n>>k;
    for(i=1; i<=k; i++)
    {
        f>>x[i];
        p=make_pair(x[i], i);
        s.insert(p);
    }
    for(i=k+1; i<=n; i++)
    {
        it=s.begin();
        S+=it->first;
        f>>x[i];
        s.insert( make_pair(x[i], i) );
        s.erase( make_pair(x[i-k], i-k) );
    }
    it=s.begin();
    S+=it->first;
    g<<S<<"\n";
    return 0;
}