#include<bits/stdc++.h>
using namespace std;

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


deque<int> q;

int v[5000010];

int main()
{
    int n,k;
    long long sum=0;

    fin>>n>>k;

    for(int i=1;i<=n;i++)
        fin>>v[i];

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

    fout<<sum;

    return 0;

}