#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

static vector<int_fast32_t> c;
static int_fast16_t n, k;

int_fast64_t mincost(int_fast16_t b, int_fast16_t e)
{
    if (e < b + 1)
        return 0;
    if (e == b + 1)
        return c[b];
    int_fast64_t mc = (int_fast64_t(1) << 63) - 1;
    int_fast64_t m;
    for (int_fast16_t kk = 0; kk < (e - b) && kk <= k; ++kk)
    {
        m = c[b + kk] + mincost(b + kk + k + 1, e);
        if (m < mc)
            mc = m;
    }
    return mc;
}

int main() {
    
    cin >> n >> k; cin.ignore();
    c.resize(n);
    for (int_fast16_t i = 0; i < n; ++i)
        cin >> c[i];
    cin.ignore();
    cout << mincost(0, n) << endl;
    return 0;
}