#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> d;
int n,k,v[5000001];
long long sum;

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