#include <algorithm>
#include <climits>
#include <fstream>
#include <deque>
std::ifstream fin("deque.in");
std::ofstream fout("deque.out");
std::deque<int> F;
int min()
{
    return *std::min_element(F.begin(),F.end());
}
int main()
{
    int N,K,X,M=INT_MAX,MP=0,SUM=0;
    fin >> N >> K;
    for (int i = 0;i<K;i++)
    {
        fin >> X;
        F.push_front(X);
    }
    M=min();
    SUM+= M;
    N-=K-1;
    for (int i = 1;i<N;i++)
    {
        F.pop_back();
        fin >> X;
        F.push_front(X);
        M=min();
        SUM+= M;
    }
    fout << SUM;
}