#include <bits/stdc++.h>
#define DimMax 5000005

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

deque<int> dqmini;

int n, k;
int v[DimMax];
long long s;

int main()
{
    fin>>n>>k;
    for(int i = 1;i <= n;i++)
        fin>>v[i];
    for(int i = 1;i <= n;i++)
    {
        while(!dqmini.empty() && v[i] <= v[dqmini.back()])
            dqmini.pop_back();
        dqmini.push_back(i);
        while(dqmini.front() <= i - k)
            dqmini.pop_front();
        if(i >= k)
            s += v[dqmini.front()];
    }
    fout<<s;
    return 0;
}