#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
long long n,k,x,s;
deque<int>dq;
vector<int>v;
int main()
{
    fin>>n>>k;
    for (int i=1;i<=n;i++)
    {
        fin>>x;
        v.push_back(x);
    }
    for(int i=0;i<n;i++)
    {
        while(!dq.empty() && v[dq.back()]>=v[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if(dq.front()<=i-k)
            dq.pop_front();
        if(i>=k-1)
            s+=v[dq.front()];
    }
    fout<<s;
}