#include <bits/stdc++.h>

using namespace std;

int main()
{
    vector<int> v;
    int n, k;
    int64_t suma=0;

    ifstream f("deque.in");
    ofstream g("deque.out");

    f>>n>>k;
    for(int i=0;i<n;++i)
    {
        int x;
        f>>x;
        v.push_back(x);
        if(i>=k-1)
        {
            for(int j=1;j<k;++j)
                if(v[i-j]<=x)
                    x=v[i-j];
            suma+=x;
        }
    }


    g<<suma;
    return 0;
}