#include <iostream>
#include <fstream>
using namespace std;

int l[5000001];
int main()
{
    ifstream f("deque.in");
    ofstream g("deque.out");
    int n, k;
    long long s =0;
    f>>n>>k;
    for (int c = 1; c <= n; c++)
    {
        f >> l[c];
    }
    int d = 1;
    while (k <= n)
    {
        int min = l[d];
        for (int c = d + 1; c <= k; c++)
        {
            if (min >= l[c])
            {
                min = l[c];
            }
        }
        k++;
        d++;
        s += min;
    }
    g<<s;
    return 0;
}