#include<iostream>
#include<fstream>
#include<vector>
#include<stack>
#include<deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,i,j,s,minn,x,minnou;
deque<int> v;
int main()
{
    fin>>n>>k;
    minn=10000000;
    for(i=1;i<=n;i++)
    {
        fin>>x;
        if(x<minn)
        {
            minn=x;
            s=s+x;
        }
        v.push_back(x);
        if(v.size()==k+1)
        {
            v.pop_front();
            minn=v.front();
            for(j=0;j<v.size();j++)
            {
                if(v[j]<minn)
                    minn=v[j];
            }
            s=s+minn;
        }
    }
    cout<<s;
    fin.close();
    fout.close();
    return 0;
}