#include <bits/stdc++.h>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");

int n,k,minn,x;
long long s=0;
deque<int>q;

void afmin()
{
    minn=INT_MAX;
    for(int i=1;i<=q.size();i++)
    {
        minn=min(minn,q.front());
        q.push_back(q.front());
        q.pop_front();
    }
}
int main()
{
    in>>n>>k;
    in>>minn;
    q.push_front(minn);
    for(int i=2;i<=n;i++)
    {
        in>>x;
        minn=min(x,minn);
        q.push_front(x);
        if(q.size()>k)
        {
            if(minn==q.back())
            {
                q.pop_back();
                afmin();
            }
            else
                q.pop_back();
            s+=minn;
        }
        else if(q.size()==k)
        {
            s+=minn;
        }
    }
    out<<s;
    return 0;
}