#include <iostream>
#include <fstream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <queue>

///#include <tryhardmode>
///#include <GODMODE::ON>

using namespace std;

#define cin fin
#define cout fout

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

const int NMAX=5e6+5;
int v[NMAX];
deque<int>dq;

int main()
{
    int n,i,j,k;
    long long s=0;
    cin>>n>>k;
    for(i=1;i<=n;i++)
        cin>>v[i];
    for(i=1;i<=n;i++)
    {
        if(!dq.empty() && dq.front()==i-k)
            dq.pop_front();
        while(!dq.empty() && v[dq.back()]>=v[i])
            dq.pop_back();
        dq.push_back(i);
        if(i>=k)
            s+=v[dq.front()];
    }
    cout<<s;
    return 0;
}