#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <cstring>
#include <deque>
#define Nmax 5000005
#define INF 0x3f3f3f3f
#define MOD 1999999973

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

int n, k;
int a[Nmax];
long long ans;
deque <int> dq;

int main()
{
    f >> n >> k;

    for (int i = 1; i <= n; i++) f >> a[i];

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

    return 0;
}