#include <iostream>
#include <fstream>
#include <deque>
#define MAXX 5000005
using namespace std;

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

int n,k,v[MAXX],sum,i;
deque <int>d;

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