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

using namespace std;

deque < pair < int , int > > q;

int main()
{
    ifstream f("deque.in");
    ofstream g("deque.out");
    int n,k;
    long long s=0;
    f>>n>>k;
    for(int i=1;i<=n;i++)
    {
        int x; f>>x;
        while(!q.empty() && q.back().first>=x)
            q.pop_back();
        q.push_back(make_pair(x,i));
        if(i-k>=0)
        {
            if(q.front().second==i-k)
                q.pop_front();
            long long val=q.front().first;
            s+=val;
        }
    }
    g<<s<<'\n';
    f.close();
    g.close();
    return 0;
}