#include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define ll long long
#define NMAX 5000005
#define INF 1000000000
#define MOD 666013

int v[NMAX];
deque<int> dq;
int main() {
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    ios::sync_with_stdio(false), cin.tie(0);
    int n, k;
    ll ans = 0;
    cin >> n >> k;
    for (int i = 1; i <= n; i++) cin >> v[i];

    for (int i = 1; i <= k; i++) {
        while (!dq.empty() && v[dq.back()] > v[i]) dq.pop_back();
        dq.push_back(i);
    }
    ans += v[dq.front()];
    for (int i = k + 1; i <= n; i++) {
        if (!dq.empty() && i - dq.front() + 1 > k) dq.pop_front();
        while (!dq.empty() && v[dq.back()] > v[i]) dq.pop_back();
        dq.push_back(i);
        ans += v[dq.front()];
    }
    cout << ans;
    return 0;
}