#include <fstream>
#include <deque>
using namespace std;
int n, k;
deque < pair <int , int> >d;
long long s;
int main()
{
ifstream f("deque.in");
ofstream g("deque.out");
f>>n>>k;
int i;
for(i=0;i<n;i++)
{
int v;
f>>v;
while(!d.empty()&& d.back().first>v )
d.pop_back();
d.push_back(make_pair( v,i ));
if( d.front().second +k==i )
d.pop_front();
s+=i<k-1? 0:d.front().first;

}
g<<s;
return 0;




}