#include <fstream>
using namespace std;
const int MAXN = 5000000;
ifstream in("deque.in");
ofstream out("deque.out");
int n,k;
int Deque[MAXN];
int p,q;
int v[MAXN];
long long rasp = 0;
void citire()
{
in >> n >> k;
for (int i = 1;i <= n;++i)
in >> v[i];
}
void prelucrare()
{
p = 1;
q = 0;
for (int i = 1;i <= n;++i)
{
while(p <= q && v[Deque[q]] >= v[i])
--q;
Deque[++q] = i;
while(Deque[p] <= i - k)
++p;
if (i >= k)
rasp += v[Deque[p]];
}
}
int main()
{
citire();
prelucrare();
out << rasp << '\n';
return 0;
}