#include <bits/stdc++.h>
#define cin ci
#define cout co
#define int long long
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int n, k, s;
vector<int> v;
deque<int> dq;
int32_t main()
{
    cin >> n >> k;
    v.resize(n+1);
    for(int i=1; i<=n; i++)
        cin >> v[i];
    for(int i=1; i<=n; i++)
    {
        while(!dq.empty() && v[dq.front()] >= v[i])
            dq.pop_front();
        dq.push_front(i);
        if(dq.back() < i - k + 1)
            dq.pop_back();
        if(i >= k)
            s += v[dq.back()];
    }
    cout << s;
    return 0;
}