#include <bits/stdc++.h>

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");
int n, k, i, r, a;
map<int, int> fr;
deque<int> q;

int main() {
    ios_base::sync_with_stdio(false);
    fin.tie(NULL);
    fin >> n >> k;
    for(i = 1; i < k; i++) {
        fin >> a;
        q.push_back(a);
        fr[a]++;
    }
    for(i = k; i <= n; i++) {
        fin >> a;
        q.push_back(a);
        fr[a]++;
        for(auto it : fr) {
            r += it.first;
            break;
        }
        if(--fr[q.front()] == 0) fr.erase(q.front());
        q.pop_front();
    }
    fout << r;

    return 0;
}