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

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

void stergere(long n, int v[]) {
    for (int i = 0; i < n; ++i)
        v[i] = v[i+1];
}

long minim (long n, int v[]) {
    int aux = v[0];
    for (long i = 1; i < n; ++i)
        if (aux > v[i])
            aux = v[i];
    return aux;
}

int main() {
    long m, n, s = 0;
    int mini;
    in >> m >> n;

    int v[n];
    for (long i = 0; i < n; ++i) {
        in >> v[i];
    }
    mini = minim(n, v);
    s += mini;

    for (long i = n; i < m ; ++i) {
        stergere(n, v);
        in >> v[n-1];
        mini = minim(n, v);
        s += mini;
    }

    out << s;

    in.close();
    out.close();
    return 0;
}