#include <bits/stdc++.h>
#define fastio std::ios_base::sync_with_stdio(NULL),cin.tie(NULL),cout.tie(NULL);
#define FILES freopen("deque.in","r",stdin);\
              freopen("deque.out","w",stdout);
#define ll long long
#define ull unsigned long long
#define ui unsigned int
#define pb push_back
#define mp make_pair
#define add emplace_back
#define MAX 5000000
#define mod 64997
#define BMAX 2048

using namespace std;
deque <int> dq;
int n,k,a,v[MAX+5];
int main()
{
    fastio
    FILES
    cin >> n >> k;
    ll ans = 0;
    for(int i = 1;i <= n; ++i)
    {
        cin >> v[i];
        while(!dq.empty() && dq.front() == i - k)
            dq.pop_front();
        while(!dq.empty() && v[dq.back()] >= v[i])
            dq.pop_back();
        dq.push_back(i);
        if(i >= k) ans += v[dq.front()];
    }
    cout << ans;
}