#include <bits/stdc++.h>
using namespace std;
# define ll long long


signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    ifstream cin("deque.in");
    ofstream cout("deque.out");

    int n, k;
    cin>>n>>k;
    vector<int> a(n);

    for(int i = 0; i < n; i++){
        cin>>a[i];
    }

    set<int> s;

    for(int i = 0; i < k; i++){
        s.insert(a[i]);
    }
    int cntMin = 0;
    ll totes = 0;
    for(int i = k; i < n; i++){
        cntMin = *(s.begin());
        totes += cntMin;
        auto it = s.find(a[i-k]);
        s.erase(it);
        s.insert(a[i]);
    }

    cntMin = *(s.begin());
    totes += cntMin;

    cout<<totes<<"\n";






    return 0;
}