#include <iostream>
#include <fstream>
#include <algorithm>
#include <deque>
#include <set>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");

const int MAXN=5e6+5;
deque < int > deq;
int n,k,v[MAXN];
long long sum;

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[i]<=v[deq.back()] ) deq.pop_back();

        deq.push_back(i);

        if(i>=k)
        {
            sum+=v[deq.front()];
            if( !deq.empty() && i-deq.front()>=k-1 ) deq.pop_front();
        }
    }
    fout<<sum;

}