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

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

deque <int>deq;
int n,k,v[5000005];
long long sum=0;
int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i];
    }
    for(int i=1;i<=n;i++)
    {
        while(!deq.empty() && v[deq.back()]>=v[i])
            deq.pop_back();
        deq.push_back(i);
        if(deq.front()<=i-k)
            deq.pop_front();
        if(i>=k)
        sum+=v[deq.front()];

    }
    fout<<sum;
    return 0;
}