#include <fstream>
#include <climits>

int v[50001];
using namespace std;

int main() {
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    int n, k, con = INT_MAX;
    long long con1 = 0LL;
    fin >> n >> k;
    for (int i = 1; i <= n; i++) {
        fin >> v[i];
    }
    for (int i = 1; i <= n - k + 1; i++) {
        for (int j = i; j < i + k; j++) {
            if (v[j] <= con)
                con = v[j];

        }
        con1 += con;
        con = INT_MAX;
    }
    fout << con1;
    fin.close();
    fout.close();
    return 0;
}