#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

deque <int>d;
int v[5000005];
int k;
long long s;

int main()
{
    ifstream be("deque.in");
    ofstream ki("deque.out");
    int n;
    be>>n>>k;
    long long s=0;
    for(int i=1;i<=n;i++)
    {
        be>>v[i];
        while(!d.empty() && d.front()<=i-k)
            d.pop_front();
        while(!d.empty() && v[d.back()]>=v[i])
            d.pop_back();
        d.push_back(i);
        if(i>=k)
            s+=v[d.front()];
    }
    ki<<s<<endl;
    return 0;
}