#include <bits/stdc++.h>

using namespace std;

int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    int n, k, x;
    cin >> n >> k;
    deque<pair<int, int> > dq;
    long long ans = 0;
    for(int i = 1; i <= n; ++i){
        cin >> x;
        while(!dq.empty() && dq.back().first > x)
            dq.pop_back();
        dq.push_back({x, i});
        while(dq.front().second <= i - k)
            dq.pop_front();
        if(i >= k)
            ans += dq.front().first;
    }
    cout << ans << '\n';
    cin.close(), cout.close();
}