#include <bits/stdc++.h>

using namespace std;
ifstream ci("deque.in");
ofstream cou("deque.out");
deque <int> dq;
int n,a[5000005],Min,k;
long long sum;
int main()
{ci >> n >> k;
for(int i=1;i<=n;i++)
   ci >> a[i];
 for(int i = 1; i <= n; i++) {
    while(!dq.empty() && a[i] <= a[dq.back()])
        dq.pop_back();
    dq.push_back(i);
    if(!dq.empty() && dq.front() <= i - k)
        dq.pop_front();
    if(i >= k)
        sum += a[dq.front()];
}

cou << sum;

    return 0;
}