#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <set>
#include <algorithm>
#include <list>
#include <map>
#include <math.h>
#define NMAX 100001
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int main() {
    deque<int>Q;
    vector<int> v;
    int n;
    int k;
    long long sumaminima=0;
    f>>n>>k;
    for(int i=1;i<=n;i++)
    {
        int x;
        f>>x;
        Q.push_back(x);
        if(i>=k)
        {
            int minim = 10000001;
            int l = k;
            while(l--)
            {
                if(Q.front() < minim)
                {
                    minim = Q.front();
                }
                v.push_back(Q.front());
                Q.pop_front();
            }
            sumaminima+=minim;
            l = k;
            while(l!=1)
            {
                Q.push_front(v.back());
                l--;
                v.pop_back();
            }
        }
    }
    g<<sumaminima;
    return 0;
}