#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

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

deque <int> d;
int v[5000010];
int64_t n,k;

int main()
{
    int64_t s=0;
    f>>n>>k;
    for (int i=1;i<=n;++i)
        f>>d[i];
    for (int64_t i=1; i<=n; ++i)
    {
        while(!d.empty() and v[i]<=v[d.back()]) d.pop_back();
        d.push_back(i);
        if(d.front()<=i-k) d.pop_front();
        if(i>=k) s+=v[d.front()];
    }
    t<<s;
    return 0;
}